Tcp/ip processor and engine using rdma

ABSTRACT

A TCP/IP processor and data processing engines for use in the TCP/IP processor is disclosed. The TCP/IP processor can transport data payloads of Internet Protocol (IP) data packets using an architecture that provides capabilities to transport and process Internet Protocol (IP) packets from Layer 2 through transport protocol layer and may also provide packet inspection through Layer 7. The engines may perform pass-through packet classification, policy processing and/or security processing enabling packet streaming through the architecture at nearly the full line rate. An application running on an initiator or target can in certain instantiations register a region of memory, which is made available to its peer(s) for access directly without substantial host intervention through RDMA data transfer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/459,349 filed on Jun. 10, 2003 titled TCP/IP Processor and EngineUsing RDMA and allowed, which claims the benefit of U.S. ProvisionalPatent Application Ser. No. 60/388,407, filed on Jun. 11, 2002 titled AHigh Performance IP Storage Processor and now expired, both of which arehereby incorporated by reference in their entirety.

This application is related to the following non-provisionalapplications, each filed on Jun. 10, 2003 claiming the benefit of U.S.Provisional Patent Application Ser. No. 60/388,407, and each of which ishereby incorporated by reference for all purposes: Ser. No. 10/458,844titled Data Processing System Using Internet Protocols, which isPending, Ser. No. 10/458,855 titled Data Processing System UsingInternet Protocols and RDMA, which is Pending, Ser. No. 10/459,019titled Memory System for a High Performance IP Processor, which isPending, Ser. No. 10/459,297 titled High Performance IP Processor, whichis Pending, Ser. No. 10/459,350 titled IP Storage Processor and EngineTherefore Using RDMA, which is Pending, and Ser. No. 10/459,674, titledHigh Performance IP Processor Using RDMA, which is Pending.

BACKGROUND OF THE INVENTION

This invention relates generally to storage networking semiconductorsand in particular to a high performance network storage processor thatis used to create Internet Protocol (IP) based storage networks.

Internet protocol (IP) is the most prevalent networking protocoldeployed across various networks like local area networks (LANs), metroarea networks (MANs) and wide area networks (WANs). Storage areanetworks (SANs) are predominantly based on Fibre Channel (FC)technology. There is a need to create IP based storage networks.

When transporting block storage traffic on IP designed to transport datastreams, the data streams are transported using Transmission ControlProtocol (TCP) that is layered to run on top of IP. TCP/IP is a reliableconnection/session oriented protocol implemented in software within theoperating systems. TCP/IP software stack is very slow to handle the highline rates that will be deployed in the future. Currently, a 1 GHzprocessor based server running TCP/IP stack, with a 1 Gbps networkconnection, would use 50-70% or more of the processor cycles, leavingminimal cycles available for the processor to allocate to theapplications that run on the server. This overhead is not tolerable whentransporting storage data over TCP/IP as well as for high performance IPnetworks. Hence, new hardware solutions would accelerate the TCP/IPstack to carry storage and network data traffic and be competitive to FCbased solutions. In addition to the TCP protocol, other protocols suchas SCTP and UDP protocols can be used, as well as other protocolsappropriate for transporting data streams.

BRIEF DESCRIPTION OF THE INVENTION

I describe a high performance hardware processor that sharply reducesthe TCP/IP protocol stack overhead from a host processor and enables ahigh line rate storage and data transport solution based on IP.

Traditionally, TCP/IP networking stack is implemented inside theoperating system kernel as a software stack. The software TCP/IP stackimplementation consumes, as mentioned above, more than 50% of theprocessing cycles available in a 1 GHz processor when serving a 1 Gbpsnetwork. The overhead comes from various aspects of the software TCP/IPstack including checksum calculation, memory buffer copy, processorinterrupts on packet arrival, session establishment, session tear downand other reliable transport services. The software stack overheadbecomes prohibitive at higher lines rates. Similar issues occur innetworks with lower line rates, like wireless networks, that use lowerperformance host processors. A hardware implementation can remove theoverhead from the host processor.

The software TCP/IP networking stack provided by the operating systemsuses up a majority of the host processor cycles. TCP/IP is a reliabletransport that can be run on unreliable data links. Hence, when anetwork packet is dropped or has errors, TCP does the retransmission ofthe packets. The errors in packets are detected using checksum that iscarried within the packet. The recipient of a TCP packet performs thechecksum of the received packet and compares that to the receivedchecksum. This is an expensive compute intensive operation performed oneach packet involving each received byte in the packet. The packetsbetween a source and destination may arrive out of order and the TCPlayer performs ordering of the data stream before presenting it to theupper layers. IP packets may also be fragmented based on the maximumtransfer unit (MTU) of the link layer and hence the recipient isexpected to defragment the packets. These functions result intemporarily storing the out of order packets, fragmented packets orunacknowledged packets in memory on the network card for example. Whenthe line rates increase to above 1 Gbps, the memory size overhead andmemory speed bottleneck resulting from these add significant cost to thenetwork cards and also cause huge performance overhead. Another functionthat consumes a lot of processor resources is the copying of the datato/from the network card buffers, kernel buffers and the applicationbuffers.

Microprocessors are increasingly achieving their high performance andspeed using deep pipelining and super scalar architectures. Interruptingthese processors on arrival of small packets will cause severeperformance degradation due to context switching overhead, pipelineflushes and refilling of the pipelines. Hence interrupting theprocessors should be minimized to the most essential interrupts only.When the block storage traffic is transported over TCP/IP networks,these performance issues become critical, severely impacting thethroughput and the latency of the storage traffic. Hence the processorintervention in the entire process of transporting storage traffic needsto be minimized for IP based storage solutions to have comparableperformance and latency as other specialized network architectures likefibre channel, which are specified with a view to a hardwareimplementation. Emerging IP based storage standards like iSCSI, FCIP,iFCP, and others (like NFS, CIFS, DAFS, HTTP, XML, XML derivatives (suchas Voice XML, EBXML, Microsoft SOAP and others), SGML, and HTML formats)encapsulate the storage and data traffic in TCP/IP segments. However,there usually isn't alignment relationship between the TCP segments andthe protocol data units that are encapsulated by TCP packets. Thisbecomes an issue when the packets arrive out of order, which is a veryfrequent event in today's networks. The storage and data blocks cannotbe extracted from the out of order packets for use until theintermediate packets in the stream arrive which will cause the networkadapters to store these packets in the memory, retrieve them and orderthem when the intermediate packets arrive. This can be expensive fromthe size of the memory storage required and also the performance thatthe memory subsystem is expected to support, particularly at line ratesabove 1 Gbps. This overhead can be removed if each TCP segment canuniquely identify the protocol data unit and its sequence. This canallow the packets to be directly transferred to their end memorylocation in the host system. Host processor intervention should also beminimized in the transfer of large blocks of data that may betransferred to the storage subsystems or being shared with otherprocessors in a clustering environment or other client serverenvironment. The processor should be interrupted only on storage commandboundaries to minimize the impact.

The IP processor set forth herein eliminates or sharply reduces theeffect of various issues outlined above through innovative architecturalfeatures and the design. The described processor architecture providesfeatures to terminate the TCP traffic carrying the storage and datapayload thereby eliminating or sharply reducing the TCP/IP networkingstack overhead on the host processor, resulting in packet streamingarchitecture that allows packets to pass through from input to outputwith minimal latency. To enable high line rate storage or data trafficbeing carried over IP requires maintaining the transmission controlblock information for various connections (sessions) that aretraditionally maintained by host kernel or driver software. As used inthis patent, the term “IP session” means a session for a sessionoriented protocol that runs on IP. Examples are TCP/IP, SCTP/IP, and thelike. Accessing session information for each packet adds significantprocessing overhead. The described architecture creates a highperformance memory subsystem that significantly reduces this overhead.The architecture of the processor provides capabilities for intelligentflow control that minimizes interrupts to the host processor primarilyat the command or data transfer completion boundary.

Today, no TCP/IP processor is offered with security.

The described processor architecture also provides integrated securityfeatures. When the storage traffic is carried on a network from theserver to the storage arrays in a SAN or other storage system, it isexposed to various security vulnerabilities that a direct attachedstorage system does not have to deal with. This processor allows for instream encryption and decryption of the storage traffic thereby allowinghigh line rates and at the same time offering confidentiality of thestorage data traffic.

Classification of network traffic is another task that consumes up tohalf of the processing cycles available on packet processors leaving fewcycles for deep packet inspection and processing. IP based storagetraffic by the nature of the protocol requires high speed low latencydeep packet processing. The described IP processor significantly reducesthe classification overhead by providing a programmable classificationengine.

Tremendous growth in the storage capacity and storage networks havecreated storage area management as a major cost item for IT departments.Policy based storage management is required to contain management costs.The described programmable classification engine allows deployment ofstorage policies that can be enforced on packet, transaction, flow andcommand boundaries. This will have significant improvement in storagearea management costs.

The programmable IP processor architecture also offers enough headroomto allow customer specific applications to be deployed. Theseapplications may belong to multiple categories e.g. network management,storage firewall or other security capabilities, bandwidth management,quality of service, virtualization, performance monitoring, zoning, LUNmasking and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a layered SCSI architecture and interaction betweenrespective layers located between initiator and target systems.

FIG. 2 illustrates the layered SCSI architecture with iSCSI and TCP/IPbased transport between initiator and target systems.

FIG. 3 illustrates an OSI stack comparison of software based TCP/IPstack with hardware oriented protocols like Fibre channel.

FIG. 4 illustrates an OSI stack with a hardware based TCP/IPimplementation for providing performance parity with the other non-IPhardware oriented protocols.

FIG. 5 illustrates a host software stack illustrating operating systemlayers implementing networking and storage stacks.

FIG. 6 illustrates software TCP stack data transfers.

FIG. 7 illustrates remote direct memory access data transfers usingTCP/IP offload from the host processor as described in this patent.

FIG. 8 illustrates host software SCSI storage stack layers fortransporting block storage data over IP networks.

FIG. 9 illustrates certain iSCSI storage network layer stack details ofan embodiment of the invention.

FIG. 10 illustrates TCP/IP network stack functional details of anembodiment of the invention.

FIG. 11 illustrates an iSCSI storage data flow through various elementsof an embodiment of the invention.

FIG. 12 illustrates iSCSI storage data structures useful in theinvention.

FIG. 13 illustrates a TCP/IP Transmission Control Block data structurefor a session database entry useful in an embodiment of the invention.

FIG. 14 illustrates an iSCSI session database structure useful in anembodiment of the invention.

FIG. 15 illustrates iSCSI session memory structure useful in anembodiment of the invention.

FIG. 16 illustrates a high-level architectural block diagram of an IPnetwork application processor useful in an embodiment of the invention.

FIG. 17 illustrates a detailed view of the architectural block diagramof the IP network application processor of FIG. 16.

FIG. 18 illustrates an input queue and controller for one embodiment ofthe IP processor.

FIG. 19 illustrates a packet scheduler, sequencer and load balanceruseful in one embodiment of the IP processor.

FIG. 20 illustrates a packet classification engine, including a policyengine block of one embodiment of the IP storage processor.

FIG. 21 broadly illustrates an embodiment of the SAN packet processorblock of one embodiment of an IP processor at a high-level.

FIG. 22 illustrates an embodiment of the SAN packet processor block ofthe described IP processor in further detail.

FIG. 23 illustrates an embodiment of the programmable TCP/IP processorengine which can be used as part of the described SAN packet processor.

FIG. 24 illustrates an embodiment of the programmable IP Storageprocessor engine which can be used as part of the described SAN packetprocessor.

FIG. 25 illustrates an embodiment of an output queue block of theprogrammable IP processor of FIG. 17.

FIG. 26 illustrates an embodiment of the storage flow controller andRDMA controller.

FIG. 27 illustrates an embodiment of the host interface controller blockof the IP processor useful in an embodiment of the invention.

FIG. 28 illustrates an embodiment of the security engine.

FIG. 29 illustrates an embodiment of a memory and controller useful inthe described processor.

FIG. 30 illustrates a data structure useable in an embodiment of thedescribed classification engine.

FIG. 31 illustrates a storage read flow between initiator and target.

FIG. 32 illustrates a read data packet flow through pipeline stages ofthe described processor.

FIG. 33 illustrates a storage write operation flow between initiator andtarget.

FIG. 34 illustrates a write data packet flow through pipeline stages ofthe described processor.

FIG. 35 illustrates a storage read flow between initiator and targetusing the remote DMA (RDMA) capability between initiator and target.

FIG. 36 illustrates a read data packet flow between initiator and targetusing RDMA through pipeline stages of the described processor.

FIG. 37 illustrates a storage write flow between initiator and targetusing RDMA capability.

FIG. 38 illustrates a write data packet flow using RDMA through pipelinestages of the described processor.

FIG. 39 illustrates an initiator command flow in more detail throughpipeline stages of the described processor.

FIG. 40 illustrates a read packet data flow through pipeline stages ofthe described processor in more detail.

FIG. 41 illustrates a write data flow through pipeline stages of thedescribed processor in more detail.

FIG. 42 illustrates a read data packet flow when the packet is in ciphertext or is otherwise a secure packet through pipeline stages of thedescribed processor.

FIG. 43 illustrates a write data packet flow when the packet is incipher text or is otherwise a secure packet through pipeline stages ofthe described processor of one embodiment of the invention.

FIG. 44 illustrates a RDMA buffer advertisement flow through pipelinestages of the described processor.

FIG. 45 illustrates a RDMA write flow through pipeline stages of thedescribed processor in more detail.

FIG. 46 illustrates a RDMA Read data flow through pipeline stages of thedescribed processor in more detail.

FIG. 47 illustrates steps of a session creation flow through pipelinestages of the described processor.

FIG. 48 illustrates steps of a session tear down flow through pipelinestages of the described processor.

FIG. 49 illustrates a session creation and session teardown steps from atarget perspective through pipeline stages of the described processor.

FIG. 50 illustrates an R2T command flow in a target subsystem throughpipeline stages of the described processor.

FIG. 51 illustrates a write data flow in a target subsystem throughpipeline stages of the described processor.

FIG. 52 illustrates a target read data flow through the pipeline stagesof the described processor.

DETAILED DESCRIPTION OF THE INVENTION

I provide a new high performance and low latency way of implementing aTCP/IP stack in hardware to relieve the host processor of the severeperformance impact of a software TCP/IP stack. This hardware TCP/IPstack is then interfaced with additional processing elements to enablehigh performance and low latency IP based storage applications. This canbe implemented in a variety of forms to provide benefits of TCP/IPtermination, high performance and low latency IP storage capabilities,remote DMA (RDMA) capabilities, security capabilities, programmableclassification and policy processing features and the like. Followingare some of the embodiments that can implement this:

Server

The described architecture may be embodied in a high performance serverenvironment providing hardware based TCP/IP functions that relieve thehost server processor or processors of TCP/IP software and performanceoverhead. The IP processor may be a companion processor to a serverchipset, providing the high performance networking interface withhardware TCP/IP. Servers can be in various form factors like bladeservers, appliance servers, file servers, thin servers, clusteredservers, database server, game server, grid computing server, VOIPserver, wireless gateway server, security server, network attachedstorage server or traditional servers. The current embodiment wouldallow creation of a high performance network interface on the servermotherboard.

Companion Processor to a Server Chipset

The server environment may also leverage the high performance IP storageprocessing capability of the described processor, besides highperformance TCP/IP and/or RDMA capabilities. In such an embodiment theprocessor may be a companion processor to a server chipset providinghigh performance network storage I/O capability besides the TCP/IPoffloading from the server processor. This embodiment would allowcreation of high performance IP based network storage I/O on themotherboard. In other words it would enable IP SAN on the motherboard.

Storage System Chipsets

The processor may also be used as a companion of a chipset in a storagesystem, which may be a storage array (or some other appropriate storagesystem or subsystem) controller, which performs the storage data serverfunctionality in a storage networking environment. The processor wouldprovide IP network storage capability to the storage array controller tonetwork in an IP based SAN. The configuration may be similar to that ina server environment, with additional capabilities in the system toaccess the storage arrays and provide other storage-centricfunctionality.

Server/Storage Host Adapter Card

The IP processor may also be embedded in a server host adapter cardproviding high speed TCP/IP networking. The same adapter card may alsobe able to offer high speed network storage capability for IP basedstorage networks. The adapter card may be used in traditional serversand may also be used as blades in a blade server configuration. Theprocessor may also be used in adapters in a storage array (or otherstorage system or subsystem) front end providing IP based storagenetworking capabilities.

Processor Chipset Component

The TCP/IP processor may be embodied inside a processor chipset,providing the TCP/IP offloading capability. Such a configuration may beused in the high end servers, workstations or high performance personalcomputers that interface with high speed networks. Such an embodimentcould also include IP storage or RDMA capabilities or combination ofthis invention to provide IP based storage networking and/or TCP/IP withRDMA capability embedded in the chipset. The usage of multiplecapabilities of the described architecture can be made independent ofusing other capabilities in this or other embodiments, as a trade-off offeature requirements, development timeline and cost, silicon die costand the like.

Storage or SAN System or Subsystem Switching Line Cards

The IP processor may also be used to create high performance, lowlatency IP SAN switching system (or other storage system or subsystem)line cards. The processor may be used as the main processor terminatingand originating IP-based storage traffic to/from the line card. Thisprocessor would work with the switching system fabric controller, whichmay act like a host, to transport the terminated storage traffic, basedon their IP destination, to the appropriate switch line card asdetermined by the forwarding information base present in the switchsystem. Such a switching system may support purely IP based networkingor may support multi-protocol support, allow interfacing with IP basedSAN along with other data center SAN fabrics like Fibre channel. A verysimilar configuration could exist inside a gateway controller system,that terminates IP storage traffic from LAN or WAN and originates newsessions to carry the storage traffic into a SAN, which may be IP basedSAN or more likely a SAN built from other fabrics inside a data centerlike Fibre channel. The processor could also be embodied in a SANgateway controller.

Storage Appliance

Storage networks management costs are increasing rapidly. The ability tomanage the significant growth in the networks and the storage capacitywould require creating special appliances which would be providing thestorage area management functionality. The described managementappliances for high performance IP based SAN, would implement my highperformance IP processor, to be able to perform its functions on thestorage traffic transported inside TCP/IP packets. These systems wouldrequire a high performance processor to do deep packet inspection andextract the storage payload in the IP traffic to provide policy basedmanagement and enforcement functions. The security, programmableclassification and policy engines along with the high speed TCP/IP andIP storage engines described would enable these appliances and otherembodiments described in this patent to perform deep packet inspectionand classification and apply the policies that are necessary on a packetby packet basis at high line rates at low latency. Further thesecapabilities can enable creating storage management appliances that canperform their functions like virtualization, policy based management,security enforcement, access control, intrusion detection, bandwidthmanagement, traffic shaping, quality of service, anti-spam, virusdetection, encryption, decryption, LUN masking, zoning, link aggregationand the like in-band to the storage area network traffic. Similar policybased management, and security operations or functionality may also besupported inside the other embodiments described in this patent.

Clustered Environments

Server systems are used in a clustered environment to increase thesystem performance and scalability for applications like clustered databases and the like. The applications running on high performance clusterservers require ability to share data at high speeds for inter-processcommunication. Transporting this inter-process communication traffic ona traditional software TCP/IP network between cluster processors suffersfrom severe performance overhead. Hence, specialized fabrics like Fibrechannel have been used in such configurations. However, a TCP/IP basedfabric which can allow direct memory access between the communicatingprocesses' memory, can be used by applications that operate on anyTCP/IP network without being changed to specialized fabrics like fibrechannel. The described IP processor with its high performance TCP/IPprocessing capability and the RDMA features, can be embodied in acluster server environment to provide the benefits of high performanceand low latency direct memory to memory data transfers. This embodimentmay also be used to create global clustering and can also be used toenable data transfers in grid computers and grid networks.

Additional Embodiments

The processor architecture can be partially implemented in software andpartially in hardware. The performance needs and cost implications candrive trade-offs for hardware and software partitioning of the overallsystem architecture of this invention. It is also possible to implementthis architecture as a combination of chip sets along with the hardwareand software partitioning or independent of the partitioning. Forexample the security processor and the classification engines could beon separate chips and provide similar functions. This can result inlower silicon cost of the IP processor including the development andmanufacturing cost, but it may in some instances increase the part countin the system and may increase the footprint and the total solutioncost. Security and classification engines could be separate chips aswell. As used herein, a chip set may mean a multiple-chip chip set, or achip set that includes only a single chip, depending on the application.

The storage flow controller and the queues could be maintained insoftware on the host or may become part of another chip in the chipset.Hence, multiple ways of partitioning this architecture are feasible toaccomplish the high performance IP based storage and TCP/IP offloadapplications that will be required with the coming high performanceprocessors in the future. The storage engine description has been givenwith respect to iSCSI, however, with TCP/IP and storage engineprogrammability, classifier programmability and the storage flowcontroller along with the control processor, other IP storage protocolslike iFCP, FCIP and others can be implemented with the appropriatefirmware. iSCSI operations may also be IP Storage operations. The highperformance IP processor core may be coupled with multiple input outputports of lower line rates, matching the total throughput to createmulti-port IP processor embodiment as well.

It is feasible to use this architecture for high performance TCP/IPoffloading from the main processor without using the storage engines.This can result in a silicon and system solution for next generationhigh performance networks for the data and telecom applications. TheTCP/IP engine can be augmented with application specific packetaccelerators and leverage the core architecture to derive new flavors ofthis processor. It is possible to change the storage engine with anotherapplication specific accelerator like a firewall engine or a routelook-up engine or a telecom/network acceleration engine, along with theother capabilities of this invention and target this processorarchitecture for telecom/networking and other applications.

Storage costs and demand have been increasing at a rapid pace over thelast several years. This is expected to grow at the same rate in theforeseeable future. With the advent of e-business, availability of thedata at any time and anywhere irrespective of the server or systemdowntime is critical. This is driving a strong need to move the serverattached storage onto a network to provide storage consolidation,availability of data and ease of management of the data. The storagearea networks (SANs) are today predominantly based on Fibre Channeltechnology, that provide various benefits like low latency and highperformance with its hardware oriented stacks compared to TCP/IPtechnology.

Some system transport block storage traffic on IP designed to transportdata streams. The data streams are transported using TransmissionControl Protocol (TCP) that is layered to run on top of IP. TCP/IP is areliable connection oriented protocol implemented in software within theoperating systems. A TCP/IP software stack is slow to handle the highline rates that will be deployed in the future. New hardware solutionswill accelerate the TCP/IP stack to carry storage and network trafficand be competitive to FC based solutions.

The prevalent storage protocol in high performance servers, workstationsand storage controllers and arrays is SCSI protocol which has beenaround for 20 years. SCSI architecture is built as layered protocolarchitecture. FIG. 1 illustrates the various SCSI architecture layerswithin an initiator, block 101, and target subsystems, block 102. Asused in patent, the terms “initiator” and “target” mean a dataprocessing apparatus, or a subsystem or system including them. The terms“initiator” and “target” can also mean a client or a server or a peer.Likewise, the term “peer” can mean a peer data processing apparatus, ora subsystem or system thereof. A “remote peer” can be a peer locatedacross the world or across the room.

The initiator and target subsystems in FIG. 1 interact with each otherusing the SCSI application protocol layer, block 103, which is used toprovide a client-server request and response transactions. It alsoprovides device service request and response between the initiator andthe target mass storage device which may take many forms like a diskarrays, tape drives, and the like. Traditionally, the target andinitiator are interconnected using the SCSI bus architecture carryingthe SCSI protocol, block 104. The SCSI protocol layer is the transportlayer that allows the client and the server to interact with each otherusing the SCSI application protocol. The transport layer must presentthe same semantics to the upper layer so that the upper layer protocolsand application can stay transport protocol independent.

FIG. 2 illustrates the SCSI application layer on top of IP basedtransport layers. An IETF standards track protocol, iSCSI (SCSI over IP)is an attempt to provide IP based storage transport protocol. There areother similar attempts including FCIP (FC encapsulated in IP), iFCP (FCover IP) and others. Many of these protocols layer on top of TCP/IP asthe transport mechanism, in a manner similar to that illustrated in FIG.2. As illustrated in FIG. 2, the iSCSI protocol services layer, block204, provides the layered interface to the SCSI application layer, block203. iSCSI carries SCSI commands and data as iSCSI protocol data units(PDUs) as defined by the standard. These protocol data units then can betransported over the network using TCP/IP, block 205, or the like. Thestandard does not specify the means of implementing the underlyingtransport that carries iSCSI PDUs. FIG. 2 illustrates iSCSI layered onTCP/IP which provides the transport for the iSCSI PDUs.

The IP based storage protocol like iSCSI can be layered in software ontop of a software based TCP/IP stack. However, such an implementationwould suffer serious performance penalties arising from software TCP/IPand the storage protocol layered on top of that. Such an implementationwould severely impact the performance of the host processor and may makethe processor unusable for any other tasks at line rates above 1 Gbps.Hence, we would implement the TCP/IP stack in hardware, relieving thehost processor, on which the storage protocol can be built. The storageprotocol, like iSCSI, can be built in software running on the hostprocessor or may, as described in this patent, be accelerated usinghardware implementation. A software iSCSI stack will present manyinterrupts to the host processor to extract PDUs from received TCPsegments to be able to act on them. Such an implementation will suffersevere performance penalties for reasons similar to those for which asoftware based TCP stack would. The described processor provides a highperformance and low latency architecture to transport Storage protocolon a TCP/IP based network that eliminates or greatly reduces theperformance penalty on the host processor, and the resulting latencyimpact.

FIG. 3 illustrates a comparison of the TCP/IP stack to Fibre channel asreferenced to the OSI networking stack. The TCP/IP stack, block 303, asdiscussed earlier in the Summary of the Invention section of thispatent, has performance problems resulting from the softwareimplementation on the hosts. Compared to that, specialized networkingprotocols like Fibre channel, block 304, and others are designed to beimplemented in hardware. The hardware implementation allows thenetworking solutions to be higher performance than the IP basedsolution. However, the ubiquitous nature of IP and the familiarity of IPfrom the IT users' and developers' perspective makes IP more suitablefor wide spread deployment. This can be accomplished if the performancepenalties resulting from TCP/IP are reduced to be equivalent to those ofthe other competing specialized protocols. FIG. 4 illustrates a protocollevel layering in hardware and software that is used for TCP/IP, block403, to become competitive to the other illustrated specializedprotocols.

FIG. 5 illustrates a host operating system stack using a hardware basedTCP/IP and storage protocol implementation of this patent. The protocolis implemented such that it can be introduced into the host operatingsystem stack, block 513, such that the operating system layers above itare unchanged. This allows the SCSI application protocols to operatewithout any change. The driver layer, block 515, and the stackunderneath for IP based storage interface, block 501, will represent asimilar interface as a non-networked SCSI interface, blocks 506 and 503or Fibre Channel interface, block 502.

FIG. 6 illustrates the data transfers involved in a software TCP/IPstack. Such an implementation of the TCP/IP stack carries hugeperformance penalties from memory copy of the data transfers. The figureillustrates data transfer between client and server networking stacks.User level application buffers, block 601, that need to be transportedfrom the client to the server or vice versa, go through the variouslevels of data transfers shown. The user application buffers on thesource get copied into the OS kernel space buffers, block 602. This datathen gets copied to the network driver buffers, block 603, from where itgets DMA-transferred to the network interface card (MC) or the host busadapter (HBA) buffers, block 604. The buffer copy operations involve thehost processor and use up valuable processor cycles. Further, the databeing transferred goes through checksum calculations on the host usingup additional computing cycles from the host. The data movement into andout of the system memory on the host multiple times creates a memorybandwidth bottleneck as well. The data transferred to the NIC/HBA isthen sent on to the network, block 609, and reaches the destinationsystem. At the destination system the data packet traverses through thesoftware networking stack in the opposite direction as the host thoughfollowing similar buffer copies and checksum operations. Suchimplementation of TCP/IP stack is very inefficient for block storagedata transfers and for clustering applications where a large amount ofdata may be transferred between the source and the destination.

FIG. 7 illustrates the networking stack in an initiator and in a targetwith features that allow remote direct memory access (RDMA) features ofthe architecture described in this patent. The following can be calledan RDMA capability or an RDMA mechanism or an RDMA function. In such asystem the application running on the initiator or target registers aregion of memory, block 702, which is made available to its peer(s) foraccess directly from the NIC/HBA without substantial host intervention.These applications would also let their peer(s) know about the memoryregions being available for RDMA, block 708. Once both peers of thecommunication are ready to use the RDMA mechanism, the data transferfrom RDMA regions can happen with essentially zero copy overhead fromthe source to the destination without substantial host intervention ifNIC/HBA hardware in the peers implement RDMA capability. The source, orinitiator, would inform its peer of its desire to read or write specificRDMA enabled buffers and then let the destination or target, push orpull the data to/from its RDMA buffers. The initiator and the targetNIC/HBA would then transport the data using the TCP/IP hardwareimplementation described in this patent, RMDA 703, TCP/IP offload 704,RMDA 708 and TCP/IP offload 709, between each other without substantialintervention of the host processors, thereby significantly reducing theprocessor overhead. This mechanism would significantly reduce the TCP/IPprocessing overhead on the host processor and eliminate the need formultiple buffer copies for the data transfer illustrated in FIG. 6. RDMAenabled systems would thus allow the system, whether fast or slow, toperform the data transfer without creating a performance bottleneck forits peer. RDMA capability implemented in this processor in storage overIP solution eliminates host intervention except usually at the datatransfer start and termination. This relieves the host processors inboth target and initiator systems, to perform useful tasks without beinginterrupted at each packet arrival or transfer. RDMA implementation alsoallows the system to be secure and prevent unauthorized access. This isaccomplished by registering the exported memory regions with the HBA/NICwith their access control keys along with the region IDs. The HBA/NICperforms the address translation of the memory region request from theremote host to the RDMA buffer, performs security operations such assecurity key verification and then allows the data transfer. Thisprocessing is performed off the host processor in the processor of thisinvention residing on the HBA/NIC or as a companion processor to thehost processor on the motherboard, for example. This capability can alsobe used for large data transfers for server clustering applications aswell as client server applications. Real time media applicationstransferring large amounts of data between a source or initiator and adestination or target can benefit from this.

FIG. 8 illustrates the host file system and SCSI stack implemented insoftware. As indicated earlier the IP based storage stack, blocks 805,806, 807, 808 and 809, should represent a consistent interface to theSCSI layers, blocks 803 and 804, as that provided by SCSI transportlayer, block 811, or Fibre channel transport, block 810. This figureillustrates high level requirements that are imposed on the IP basedstorage implementation from a system level, besides those imposed byvarious issues of IP which is not designed to transport performancesensitive block data.

FIG. 9 illustrates the iSCSI stack in more detail from that illustratedin FIG. 8. The iSCSI stack blocks 805 though 809, should provide an OSdefined driver interface level functionality to the SCSI commandconsolidation layer blocks 803 & 804, such that the behavior of thislayer and other layers on top of it are unchanged. FIG. 9 illustrates aset of functions that would be implemented to provide IP storagecapabilities. The functions that provide the iSCSI functionality aregrouped into related sets of functions, although there can be manyvariations of these as any person skilled in this area would appreciate.There are a set of functions that are required to meet the standard(e.g. target and initiator login and logout) functions, block 916,connection establishment and teardown functions, block 905. The figureillustrates functions that allow the OS SCSI software stack to discoverthe iSCSI device, block 916, set and get options/parameters, blocks 903and 909, to start the device, block 913 and release the device, block911. Besides the control functions discussed earlier, the iSCSIimplementation provides bulk data transfer functions, through queues 912and 917, to transport the PDUs specified by the iSCSI standard. TheiSCSI stack may also include direct data transfer/placement (DDT) orRDMA functions or combination thereof, block 918, which are used by theinitiator and target systems to perform substantially zero buffer copyand host intervention-less data transfers including storage and otherbulk block data transfers. The SCSI commands and the block datatransfers related to these are implemented as command queues, blocks 912and 917, which get executed on the described processor. The host isinterrupted primarily on the command completion. The completed commandsare queued for the host to act on at a time convenient to the host. Thefigure illustrates the iSCSI protocol layer and the driver layer layeredon the TCP/IP stack, blocks 907 and 908, which is also implemented offthe host processor on the IP processor system described herein.

FIG. 10 illustrates the TCP/IP stack functionality that is implementedin the described IP processor system. These functions provide aninterface to the upper layer protocol functions to carry the IP storagetraffic as well as other applications that can benefit from direct OSTCP/IP bypass, RDMA or network sockets direct capabilities orcombination thereof to utilize the high performance TCP/IPimplementation of this processor. The TCP/IP stack provides capabilitiesto send and receive upper layer data, blocks 1017 and 1031, and commandPDUs, establish the transport connections and teardown functions, block1021, send and receive data transfer functions, checksum functions,block 1019, as well as error handling functions, block 1022, andsegmenting and sequencing and windowing operations, block 1023. Certainfunctions like checksum verification/creation touch every byte of thedata transfer whereas some functions that transport the data packets andupdate the transmission control block or session data base are invokedfor each packet of the data transfer. The session DB, block 1025, isused to maintain various information regarding the activesessions/connections along with the TCP/IP state information. The TCPlayer is built on top of IP layer that provides the IP functionality asrequired by the standard. This layer provides functions tofragment/de-fragment, block 1033, the packets as per the path MTU,providing the route and forwarding information, block 1032, as well asinterface to other functions necessary for communicating errors like,for example, ICMP, block 1029. The IP layer interfaces with the Ethernetlayer or other media access layer technology to transport the TCP/IPpackets onto the network. The lower layer is illustrated as Ethernet invarious figures in this description, but could be other technologieslike SONET, for instance, to transport the packets over SONET onMANs/WANs. Ethernet may also be used in similar applications, but may beused more so within a LAN and dedicated local SAN environments, forexample.

FIG. 11 illustrates the iSCSI data flow. The figure illustrates thereceive and transmit path of the data flow. The Host's SCSI commandlayer working with the iSCSI driver, both depicted in block 1101, wouldschedule the commands to be processed to the command scheduler, block1108, in the storage flow controller seen in more detail in FIG. 26. Thecommand scheduler 1108 schedules the new commands for operation in theprocessor described in more detail in FIG. 17. A new command that ismeant for the target device with an existing connection gets en-queuedto that existing connection, block 1111. When the connection to thetarget device does not exist, a new command is en-queued on to theunassigned command queue, block 1102. The session/connectionestablishment process like that shown in FIG. 47 and blocks 905 and 1006is then called to connect to the target. Once the connection isestablished the corresponding command from the queue 1102 gets en-queuedto the newly created connection command queue 1111 by the commandscheduler 1108 as illustrated in the figure. Once a command reaches astage of execution, the receive 1107 or transmit 1109 path is activateddepending on whether the command is a read or a write transaction. Thestate of the connection/session which the command is transported is usedto record the progress of the command execution in the session databaseas described subsequently. The buffers associated with the data transfermay be locked till such time as the transfer is completed. If the RDMAmechanism is used to transfer the data between the initiator and thetarget, appropriate region buffers identifiers, access control keys andrelated RDMA state data is maintained in memory on board the processorand may also be maintained in off-chip memory depending on theimplementation chosen. As the data transfer, which may be over multipleTCP segments, associated with the command is completed the status of thecommand execution is passed onto the host SCSI layer which then does theappropriate processing. This may involve releasing the buffers beingused for data transfers to the applications, statistics update, and thelike. During transfer, the iSCSI PDUs are transmitted by the transmitengines, block 1109, working with the transmit command engines, block1110, that interpret the PDU and perform appropriate operations likeretrieving the application buffers from the host memory using DMA to thestorage processor and keeping the storage command flow information inthe iSCSI connection database updated with the progress. As used in thispatent the term “engine” can be a data processor or a part of a dataprocessor, appropriate for the function or use of the engine. Similarly,the receive engines, block 1107, interpret the received command into newrequests, response, errors or other command or data PDUs that need to beacted on appropriately. These receive engines working with the commandengines, block 1106, route the read data or received data to theappropriate allocated application buffer through direct datatransfer/placement or RDMA control information maintained for thesession in the iSCSI session table. On command completion the control tothe respective buffers, blocks 1103 and 1112, is released for theapplication to use. Receive and transmit engines can be the SAN packetprocessors 1706(a) to 1706(n) of FIG. 17 of this IP processor workingwith the session information recorded in the session data base entries1704, which can be viewed as a global memory as viewed from the TCP/IPprocessor of FIG. 23 or the IP processor of FIG. 24 The same engines canget reused for different packets and commands with the appropriatestorage flow context provided by the session database discussed in moredetail below with respect to block 1704 and portion of session databasein 1708 of FIG. 17. For clarification, the terms IP network applicationprocessor, IP Storage processor, IP Storage network applicationprocessor and IP processor can be the same entity, depending on theapplication. An IP network application processor core or an IP storagenetwork application processor core can be the same entity, depending onthe application.

Similarly a control command can use the transmit path whereas thereceived response would use the receive path. Similar engines can existon the initiator as well as the target. The data flow direction isdifferent depending on whether it is the initiator or the target.However, primarily similar data flow exists on both initiator and targetwith additional steps at the target. The target needs to performadditional operations to reserve the buffers needed to get the data of awrite command, for instance, or may need to prepare the read data beforethe data is provided to the initiator. Similar instances would exist incase of an intermediate device, although, in such a device, which may bea switch or an appliance, some level of virtualization or framefiltering or such other operation may be performed that may requiretermination of the session on one side and originating sessions on theother. This functionality is supported by this architecture but notillustrated explicitly in this figure, inasmuch as it is well within theknowledge of one of ordinary skill in the art.

FIG. 12 through FIG. 15 illustrate certain protocol informationregarding transport sessions and how that information may be stored in adatabase in memory.

FIG. 12 illustrates the data structures that are maintained for iSCSIprotocol and associated TCP/IP connections. The data belonging to eachiSCSI session, block 1201, which is essentially a nexus of initiator andtarget connections, is carried on the appropriate connection, block1202. Dependent commands are scheduled on the queues of the sameconnection to maintain the ordering of the commands, block 1203.However, unrelated commands can be assigned to different transportconnection. It is possible to have all the commands be queued to thesame connection, if the implementation supports only one connection persession. However, multiple connections per session are feasible tosupport line trunking between the initiator and the target. For example,in some applications, the initiator and the target will be incommunication with each other and will decide through negotiation toaccept multiple connections. In others, the initiator and target willcommunicate through only one session or connection. FIG. 13 and FIG. 14illustrate the TCP/IP and iSCSI session data base or transmissioncontrol block per session and connection. These entries may be carriedas separate tables or may be carried together as a composite table asseen subsequently with respect to FIGS. 23, 24, 26 and 29 depending onthe implementation chosen and the functionality implemented e.g. TCP/IPonly, TCP/IP with RDMA, IP Storage only, IP storage with TCP/IP, IPStorage with RDMA and the like. Various engines that perform TCP/IP andstorage flow control use all or some of these fields or more fields notshown, to direct the block data transfer over TCP/IP. The appropriatefields are updated as the connection progresses through the multiplestates during the course of data transfer. FIG. 15 illustrates onemethod of storing the transmission control entries in a memory subsystemthat consists of an on-chip session cache, blocks 1501 and 1502, andoff-chip session memory, blocks 1503, 1504, 1505, 1506 and 1507, thatretains the state information necessary for continuous progress of thedata transfers.

FIG. 16 illustrates the IP processor architecture at a high level ofabstraction. The processor consists of modular and scalable IP networkapplication processor core, block 1603. Its functional blocks providethe functionality for enabling high speed storage and data transportover IP networks. The processor core can include an intelligent flowcontroller, a programmable classification engine and a storage/networkpolicy engine. Each can be considered an individual processor or anycombination of them can be implemented as a single processor. Thedisclosed processor also includes a security processing block to providehigh line rate encryption and decryption functionality for the networkpackets. This, likewise, can be a single processor, or combined with theothers mentioned above. The disclosed processor includes a memorysubsystem, including a memory controller interface, which manages the onchip session cache/memory, and a memory controller, block 1602, whichmanages accesses to the off chip memory which may be SRAM, DRAM, FLASH,ROM, EEPROM, DDR SDRAM, RDRAM, FCRAM, QDR SRAM, or other derivatives ofstatic or dynamic random access memory or a combination thereof. The IPprocessor includes appropriate system interfaces to allow it to be usedin the targeted market segments, providing the right media interfaces,block 1601, for LAN, SAN, WAN and MAN networks, and similar networks,and appropriate host interface, block 1606. The media interface blockand the host interface block may be in a multi-port form where some ofthe ports may serve the redundancy and fail-over functions in thenetworks and systems in which the disclosed processor is used. Theprocessor also may contain the coprocessor interface block 1605, forextending the capabilities of the main processor for example creating amulti-processor system. The system controller interface of block 1604allows this processor to interface with an off-the-shelf microcontrollerthat can act as the system controller for the system in which thedisclosed processor may be used. The processor architecture also supporta control plane processor on board, that could act as the systemcontroller or session manager. The system controller interface may stillbe provided to enable the use of an external processor. Such a versionof this processor may not include the control processor for die costreasons. There are various types of the core architecture that can becreated, targeting specific system requirements, for example serveradapters or storage controllers or switch line cards or other networkingsystems. The primary differences would be as discussed in the earliersections of this patent. These processor blocks provide capabilities andperformance to achieve the high performance IP based storage usingstandard protocols like iSCSI, FCIP, iFCP and the like. The detailedarchitecture of these blocks will be discussed in the followingdescription.

FIG. 17 illustrates the IP processor architecture in more detail. Thearchitecture provides capabilities to process incoming IP packets fromthe media access control (MAC) layer, or other appropriate layer,through full TCP/IP termination and deep packet inspection. This blockdiagram does not show the MAC layer block 1601, or blocks 1602, 1604 or1605 of FIG. 16. The MAC layer interface blocks to the input queue,block 1701, and output queue, block 1712, of the processor in the mediainterface, block 1601, shown in FIG. 16. The MAC functionality could bestandards based, with the specific type dependent on the network.Ethernet and Packet over SONET are examples of the most widely usedinterfaces today which may be included on the same silicon or adifferent version of the processor created with each.

The block diagram in FIG. 17 illustrates input queue and output queueblocks 1701 and 1712 as two separate blocks. The functionality may beprovided using a combined block. The input queue block 1701 consists ofthe logic, control and storage to retrieve the incoming packets from theMAC interface block. Block 1701 queues the packets as they arrive fromthe interface and creates appropriate markers to identify start of thepacket, end of the packet and other attributes like a fragmented packetor a secure packet, and the like, working with the packet scheduler 1702and the classification engine 1703. The packet scheduler 1702, canretrieve the packets from the input queue controller and passes them forclassification to the classification engine. The classification block1703, is shown to follow the scheduler, however from a logicalperspective the classification engine receives the packet from the inputqueue, classifies the packet and provides the classification tag to thepacket, which is then scheduled by the scheduler to the processor array1706(a) . . . 1706(n). Thus the classification engine can act as apass-through classification engine, sustaining the flow of the packetsthrough its structure at the full line rate. The classification engineis a programmable engine that classifies the packets received from thenetwork in various categories and tags the packet with theclassification result for the scheduler and the other packet processorsto use. Classification of the network traffic is a very computeintensive activity which can take up to half of the processor cyclesavailable in a packet processor. This integrated classification engineis programmable to perform Layer 2 through Layer 7 inspection. Thefields to be classified are programmed in with expected values forcomparison and the action associated with them if there is a match. Theclassifier collects the classification walk results and can presentthese as a tag to the packet identifying the classification result asseen subsequently with respect to FIG. 30. This is much like a treestructure and is understood as a “walk.” The classified packets are thenprovided to the scheduler 1702 as the next phase of the processingpipeline.

The packet scheduler block 1702 includes a state controller andsequencer that assign packets to appropriate execution engines on thedisclosed processor. The execution engines are the SAN packetprocessors, block 1706(a) through 1706(n), including the TCP/IP and/orstorage engines as well as the storage flow/RDMA controller, block 1708or host bypass and/or other appropriate processors, depend on thedesired implementation. For clarity, the term “/”, when used todesignate hardware components in this patent, can mean “and/or” asappropriate. For example, the component “storage flow/RDMA controller”can be a storage flow and RDMA controller, a storage flow controller, oran RDMA controller, as appropriate for the implementation. The scheduler1702 also maintains the packet order through the processor where thestate dependency from a packet to a packet on the sameconnection/session is important for correct processing of the incomingpackets. The scheduler maintains various tables to track the progress ofthe scheduled packets through the processor until packet retirement. Thescheduler also receives commands that need to be scheduled to the packetprocessors on the outgoing commands and packets from the host processoror switch fabric controller or interface.

The TCP/IP and storage engines along with programmable packet processorsare together labeled as the SAN Packet Processors 1706(a) through1706(n) in FIG. 17. These packet processors are engines that areindependent programmable entities that serve a specific role.Alternatively, two or more of them can be implemented as a singleprocessor depending on the desired implementation. The TCP/IP engine ofFIG. 23 and the storage engines of FIG. 24 are configured in thisexample as coprocessors to the programmable packet processor engineblock 2101 of FIG. 21. This architecture can thus be applied withrelative ease to applications other than storage bysubstituting/removing for the storage engine for reasons of cost,manufacturability, market segment and the like. In a pure networkingenvironment the storage engine could be removed, leaving the packetprocessor with a dedicated TCP/IP engine and be applied for thenetworking traffic, which will face the same processing overhead fromTCP/IP software stacks. Alternatively one or more of the engines may bedropped for desired implementation e.g. for processor supporting only IPStorage functions may drop TCP/IP engine and/or packet engine which maybe in a separate chip. Hence, multiple variations of the core scalableand modular architecture are possible. The core architecture can thus beleveraged in applications beside the storage over IP applications bysubstituting the storage engine with other dedicated engines, forexample a high performance network security and policy engine, a highperformance routing engine, a high performance network managementengine, deep packet inspection engine providing string search, an enginefor XML, an engine for virtualization, and the like, providing supportfor an application specific acceleration. The processing capability ofthis IP processor can be scaled by scaling the number of SAN PacketProcessor blocks 1706 (a) through 1706 (n) in the chip to meet the linerate requirements of the network interface. The primary limitation fromthe scalability would come from the silicon real-estate required and thelimits imposed by the silicon process technologies. Fundamentally thisarchitecture is scalable to very high line rates by adding more SANpacket processor blocks thereby increasing the processing capability.Other means of achieving a similar result is to increase the clockfrequency of operation of the processor to that feasible within theprocess technology limits.

FIG. 17 also illustrates the IP session cache/memory and the memorycontroller block 1704. This cache can be viewed as an internal memory orlocal session database cache. This block is used to cache and store theTCP/IP session database and also the storage session database for acertain number of active sessions. The number of sessions that can becached is a direct result of the chosen silicon real-estate and what iseconomically feasible to manufacture. The sessions that are not on chip,are stored and retrieved to/from off chip memory, viewed as an externalmemory, using a high performance memory controller block which can bepart of block 1704 or otherwise. Various processing elements of thisprocessor share this controller using a high speed internal bus to storeand retrieve the session information. The memory controller can also beused to temporarily store packets that may be fragmented or when thehost interface or outbound queues are backed-up. The controller may alsobe used to store statistics information or any other information thatmay be collected by the disclosed processor or the applications runningon the disclosed or host processor.

The processor block diagram of FIG. 17 also illustrates host interfaceblock 1710, host input queue, block 1707 and host output queue, block1709 as well as the storage flow/RDMA controller, block 1708. Theseblocks provide the functions that are required to transfer data to andfrom the host (also called “peer”) memory or switch fabric. These blocksalso provide features that allow the host based drivers to schedule thecommands, retrieve incoming status, retrieve the session database entry,program the disclosed processor, and the like to enable capabilitieslike sockets direct architecture, full TCP/IP termination, IP storageoffload and the like capabilities with or without using RDMA. The hostinterface controller 1710, seen in greater detail in FIG. 27, providesthe configuration registers, DMA engines for direct memory to memorydata transfer, the host command block that performs some of the abovetasks, along with the host interface transaction controller and the hostinterrupt controller. The host input and output queues 1707, 1709provide the queuing for incoming and outgoing packets. The storage flowand RDMA controller block 1708 provides the functionality necessary forthe host to queue the commands to the disclosed processor, which thentakes these commands and executes them, interrupting the host processoron command termination. The RDMA controller portion of block 1708provides various capabilities necessary for enabling remote directmemory access. It has tables that include information such as RDMAregion, access keys, and virtual address translation functionality. TheRDMA engine inside this block performs the data transfer and interpretsthe received RDMA commands to perform the transaction if the transactionis allowed. The storage flow controller of block 1708 also keeps trackof the state of the progress of various commands that have beenscheduled as the data transfer happens between the target and theinitiator. The storage flow controller schedules the commands forexecution and also provides the command completion information to thehost drivers. The above can be considered RDMA capability and can beimplemented as described or by implementing as individual processors,depending on designer's choice. Also, additional functions can be addedto or removed from those described without departing from the spirit orthe scope of this patent.

The control plane processor block 1711 of this processor is used toprovide relatively slow path functionality for TCP/IP and/or storageprotocols which may include error processing with ICMP protocol, nameresolution, address resolution protocol, and it may also be programmedto perform session initiation/teardown acting as a sessioncontroller/connection manger, login and parameter exchange, and thelike. This control plane processor could be off chip to provide thesystem developer a choice of the control plane processor, or may be onchip to provide an integrated solution. If the control plane processoris off-chip, then an interface-block would be created or integratedherein that would allow this processor to interface with the controlplane processor and perform data and command transfers. The internal busstructures and functional block interconnections may be different thanillustrated for all the detailed figures for performance, die costrequirements and the like and not depart from the spirit and the scopeof this patent.

Capabilities described above for FIG. 17 blocks with more detail below,enable a packet streaming architecture that allows packets to passthrough from input to output with minimal latency, with in-streamprocessing by various processing resources of the disclosed processor.

FIG. 18 illustrates the input queue and controller block shown generallyat 1701 of FIG. 17 in more detail. The core functionality of this blockis to accept the incoming packets from multiple input ports, Ports 1 toN, in blocks 1801 and 1802(i) to 1802(n), and to queue them using afixed or programmable priority on the input packet queue, block 1810,from where the packets get dequeued for classifier, scheduler andfurther packet processing through scheduler I/F blocks 1807-1814. Theinput queue controller interfaces with each of the input ports (Port 1through Port N in a multi-port implementation), and queues the packetsto the input packet queue 1810. The packet en-queue controller andmarker block 1804 may provide fixed priority functions or may beprogrammable to allow different policies to be applied to differentinterfaces based on various characteristics like port speed, the networkinterface of the port, the port priority and others that may beappropriate. Various modes of priority may be programmable likeround-robin, weighted round-robin or others. The input packet de-queuecontroller 1812 de-queues the packets and provides them to the packetscheduler, block 1702 of FIG. 17 via scheduler I/F 1814. The schedulerschedules the packets to the SAN packet processors 1706 (a)-1706 (n)once the packets have been classified by the classification engine 1703of FIG. 17. The encrypted packets can be classified as encrypted firstand passed on to the security engine 1705 of FIG. 17 by the securepacket interface block 1813 of FIG. 18, for authentication and/ordecryption if the implementation includes security processing otherwisethe security interfaces may not be present and an external securityprocessor would be used to perform similar functions. The decryptedpackets from clear packet interface, block 1811, are then provided tothe input queue through block 1812 from which the packet follows thesame route as a clear packet. The fragmented IP packets may be storedon-chip in the fragmented packet store and controller buffers, block1806, or may be stored in the internal or external memory. When the lastfragment arrives, the fragment controller of block 1806, working withthe classification engine and the scheduler of FIG. 17, merges thesefragments to assemble the complete packet. Once the fragmented packet iscombined to form a complete packet, the packet is scheduled into theinput packet queue via block 1804 and is then processed by the packetde-queue controller, block 1812, to be passed on to various otherprocessing stages of this processor. The input queue controller of FIG.18 assigns a packet tag/descriptor to each incoming packet which ismanaged by the attribute manager of block 1809 which uses the packetdescriptor fields like the packet start, size, buffer address, alongwith any other security information from classification engine, andstored in the packet attributes and tag array of block 1808. The packettag and attributes are used to control the flow of the packet throughthe processor by the scheduler and other elements of the processor in anefficient manner through interfaces 1807, 1811, 1813 and 1814

FIG. 19 illustrates the packet scheduler and sequencer 1702 of FIG. 17in more detail. This block is responsible for scheduling packets andtasks to the execution resources of this processor and thus also acts asa load balancer. The scheduler retrieves the packet headers from theheader queue, block 1902, from the input queue controller 1901 to passthem to the classification engine 1703 of February 17 which returns theclassification results to the classifier queue, block 1909, that arethen used by the rest of the processor engines. The classificationengine may be presented primarily with the headers, but if deep packetinspection is also programmed, the classification engine may receive thecomplete packets which it routes to the scheduler after classification.The scheduler comprises a classification controller/scheduler, block1908, which manages the execution of the packets through theclassification engine. This block 1908 of FIG. 19 provides the commandsto the input queue controller, block 1901, in case of fragmented packetsor secure packets, to perform the appropriate actions for such packetse.g. schedule an encrypted packet to the security engine of FIG. 17. Thescheduler state control and the sequencer, block 1916, receive stateinformation of various transactions/operations active inside theprocessor and provide instructions for the next set of operations. Forinstance, the scheduler retrieves the packets from the input packetqueue of block 1903, and schedules these packets in the appropriateresource queue depending on the results of the classification receivedfrom the classifier or directs the packet to the packet memory, block1913 or 1704 through 1906, creating a packet descriptor/tag which may beused to retrieve the packet when appropriate resource needs it toperforms its operations at or after scheduling. The state control andsequencer block 1916 instructs/directs the packets with theirclassification result, block 1914, to be stored in the packet memory,block 1913, from where the packets get retrieved when they are scheduledfor operation. The state controller and the sequencer identify theexecution resource that should receive the packet for operation andcreates a command and assigns this command with the packet tag to theresource queues, blocks 1917 (Control Plane), 1918 (port i-port n), 1919(bypass) and 1920 (host) of FIG. 19. The priority selector 1921 is aprogrammable block that retrieves the commands and the packet tag fromthe respective queues based on the assigned priority and passes this tothe packet fetch and command controller, block 1922. This blockretrieves the packet from the packet memory store 1913 along with theclassification results and schedules the packet transfer to theappropriate resource on the high performance processor command andpacket busses such as at 1926 when the resource is ready for operation.The bus interface blocks, like command bus interface controller 1905, ofthe respective recipients interpret the command and accept the packetand the classification tag for operation. These execution engines informthe scheduler when the packet operation is complete and when the packetis scheduled for its end destination (either the host bus interface, orthe output interface or control plane interface, etc.). This allows thescheduler to retire the packet from its state with the help ofretirement engine of block 1904 and frees up the resource entry for thissession in the resource allocation table, block 1923. The resourceallocation table is used by the sequencer to assign the received packetsto specific resources, depending on the current state of internal stateof these resources, e.g. the session database cache entry buffered inthe SAN packet processor engine, the connection ID of the current packetbeing executed in the resource, and the like. Thus packets that aredependent on an ordered execution get assigned primarily to the sameresource, which improves memory traffic and performance by using thecurrent DB state in the session memory in the processor and not have toretrieve new session entries. The sequencer also has interface to thememory controller, block 1906, for queuing of packets that arefragmented packets and/or for the case in which the scheduler queues getbacked-up due to a packet processing bottleneck down stream, which maybe caused by specific applications that are executed on packets thattake more time than that allocated to maintain a full line rateperformance, or for the case in which any other downstream systems getfull, unable to sustain the line rate.

If the classifier is implemented before the scheduler as discussed abovewith respect to FIG. 17 where the classification engine receives thepacket from the input queue, items 1901, 1902, 1908, 1909 and 1910 wouldbe in the classifier, or may not be needed, depending on the particulardesign. The appropriate coupling from the classifier to/from thescheduler blocks 1903, 1907, 1914 and 1915 may be created in such ascenario and the classifier coupled directly to the input queue block ofFIG. 18.

FIG. 20 illustrates the packet classification engine shown generally at1703 of FIG. 17. Classification of the packets into their variousattributes is a very compute intensive operation. The classifier can bea programmable processor that examines various fields of the receivedpacket to identify the type of the packet, the protocol type e.g. IP,ICMP, TCP, UDP etc, the port addresses, the source and destinationfields, etc. The classifier can be used to test a particular field or aset of fields in the header or the payload. The block diagramillustrates a content addressable memory based classifier. However, asdiscussed earlier this could be a programmable processor as well. Theprimary differences are the performance and complexity of implementationof the engine. The classifier gets the input packets through thescheduler from the input queues, blocks 2005 and 2004 of FIG. 20. Theinput buffers 2004 queue the packets/descriptor and/or the packetheaders that need to be classified. Then the classification sequencer2003 fetches the next available packet in the queue and extracts theappropriate packet fields based on the global field descriptor sets,block 2007, which are, or can be, programmed. Then the classifier passesthese fields to the content addressable memory (CAM) array, block 2009,to perform the classification. As the fields are passed through the CAMarray, the match of these fields identifies next set of fields to becompared and potentially their bit field location. The match in the CAMarray results in the action/event tag, which is collected by the resultcompiler, (where “compiling” is used in the sense of “collecting”) block2014 and also acted on as an action that may require updating the datain the memory array, block 2013, associated with specific CAM conditionor rule match. This may include performing an arithmetic logic unit(ALU) operation, block 2017, which can be considered one example of anexecution resource) on this field e.g. increment or decrement thecondition match and the like. The CAM arrays are programmed with thefields, their expected values and the action on match, including nextfield to compare, through the database initialization block 2011,accessible for programming through the host or the control planeprocessor interfaces 1710, 1711. Once the classification reaches a leafnode the classification is complete and the classification tag isgenerated that identifies the path traversed that can then be used byother engines of the IP processor avoid performing the sameclassification tasks. For example a classification tag may include theflow or session ID, protocol type indication e.g. TCP/UDP/ICMP etc.,value indicating whether to processes, bypass, drop packet, dropsession, and the like, or may also include the specific firmware coderoutine pointer for the execution resource to start packet processing ormay include signature of the classification path traversed or the like.The classification tag fields are chosen based on processorimplementation and functionality. The classifier retirement queue, block2015, holds the packets/descriptors of packets that are classified andclassification tag and are waiting to be retrieved by the scheduler. Theclassification data base can be extended using database extensioninterface and pipeline control logic block 2006. This allows systemsthat need extensibility for a larger classification database to bebuilt. The classification engine with the action interpreter, the ALUand range matching block of 2012 also provide capabilities to programstorage/network policies/actions that need to be taken if certainpolicies are met. The policies can be implemented in the form of ruleand action tables. The policies get compiled and programmed in theclassification engine through the host interface along with theclassification tables. The database interface and pipeline control 2006could be implemented to couple to companion processor to extend the sizeof the classification/policy engine.

FIG. 21 illustrates the SAN Packet Processor shown generally at 1706 (a)through 1706 (n) of FIG. 17. A packet processor can be a speciallydesigned packet processor, or it can be any suitable processor such asan ARM, MIPS, StrongARM, X86, PowerPC, Pentium processor, or any otherprocessor that serves the functions described herein. This is alsoreferred as the packet processor complex in various sections of thispatent. This packet processor comprises a packet engine, block 2101,which is generally a RISC machine with target instructions for packetprocessing or a TCP/IP engine, block 2102 or an IP storage engine, block2103 or a combination thereof. These engines can be configured ascoprocessors to the packet engine or can be independent engines. FIG. 22illustrates the packet engine in more detail. The packet engine is agenerally RISC machine as indicated above with instruction memory, block2202, and Data Memory, block 2206, (both of which can be RAM) that areused to hold the packet processing micro routines and the packets andintermediate storage. The instruction memory 2202 which, like all suchmemory in this patent, can be RAM or other suitable storage, isinitialized with the code that is executed during packet processing. Thepacket processing code is organized as tight micro routines that fitwithin the allocated memory. The instruction decoder and the sequencer,block 2204, fetches the instructions from instruction memory 2202,decodes them and sequences them through the execution blocks containedwithin the ALU, block 2208. This machine can be a simple pipelinedengine or a more complex deep pipelined machine that may also bedesigned to provide a packet oriented instruction set. The DMA engine,block 2205 and the bus controller, block 2201, allow the packet engineto move the data packets from the scheduler of FIG. 19 and the hostinterface into the data memory 2206 for operation. The DMA engine mayhold multiple memory descriptors to store/retrieve packet/data to/fromhost memory/packet memory. This would enable memory accesses to happenin parallel to packet processor engine operations. The DMA engine 2205also may be used to move the data packets to and from the TCP andstorage engines 2210, 2211. Once the execution of the packet iscomplete, the extracted data or newly generated packet is transferred tothe output interface either towards the media interface or the hostinterface.

FIG. 23 illustrates a programmable TCP/IP packet processor engine, seengenerally at 2210 of FIG. 22, in more detail. This engine is generally aprogrammable processor with common RISC instructions along with variousTCP/IP oriented instructions and execution engines but could also be amicro-coded or a state machine driven processor with appropriateexecution engines described in this patent. The TCP processor includes achecksum block, 2311, for TCP checksum verification and new checksumgeneration by executing these instructions on the processor. Thechecksum block extracts the data packet from the packet buffer memory (aData RAM is one example of such memory), 2309, and performs the checksumgeneration or verification. The packet look-up interface block, 2310,assists the execution engines and the instruction sequencer, 2305,providing access to various data packet fields or the full data packet.The classification tag interpreter, 2313, is used by the instructiondecoder 2304 to direct the program flow based on the results of theclassification if such an implementation is chosen. The processorprovides specific sequence and windowing operations includingsegmentation, block 2315, for use in the TCP/IP data sequencingcalculations for example, to look-up the next expected sequence numberand see if that received is within the agreed upon sliding window, whichsliding window is a well known part of the TCP protocol, for theconnection to which the packet belongs. This element 2315 may alsoinclude a segmentation controller like that show at 2413 of FIG. 24.Alternatively, one of ordinary skill in the art, with the teaching ofthis patent, can easily implement the segmentation controllers elsewhereon the TCP/IP processor of this FIG. 23. The processor provides a hashengine, block 2317, which is used to perform hash operations againstspecific fields of the packet to perform a hash table walk that may berequired to get the right session entry for the packet. The processoralso includes a register file, block 2316, which extracts variouscommonly used header fields for TCP processing, along with pointerregisters for data source and destination, context register sets, andregisters that hold the TCP states along with a general purpose registerfile. The TCP/IP processor can have multiple contexts for packetexecution, so that when a given packet execution stalls for any reason,for example memory access, the other context can be woken up and theprocessor continue the execution of another packet stream with littleefficiency loss. The TCP/IP processor engine also maintains a localsession cache, block 2320, which holds most recently used or mostfrequently used entries, which can be used locally without needing toretrieve them from the global session memory. The local session cachecan be considered an internal memory of the TCP/IP processor, which canbe a packet processor. Of course, the more entries that will be usedthat can be stored locally in the internal memory, without retrievingadditional ones from the session, or global, memory, the more efficientthe processing will be. The packet scheduler of FIG. 19 is informed ofthe connection IDs that are cached per TCP/IP processor resource, sothat it can schedule the packets that belong to the same session to thesame packet processor complex. When the packet processor does not holdthe session entry for the specific connection, then the TCP sessiondatabase lookup engine, block 2319, working with the session manager,block 2321, and the hash engine retrieves the corresponding entry fromthe global session memory through the memory controller interface, block2323. There are means, such as logic circuitry inside the sessionmanager that allow access of session entries or fields of sessionentries, that act with the hash engine to generate the sessionidentifier for storing/retrieving the corresponding session entry or itsfields to the session database cache. This can be used to update thosefields or entries as a result of packet processing. When a new entry isfetched, the entry which it is replacing is stored to the global sessionmemory. The local session caches may follow exclusivity cachingprinciples, so that multiple processor complexes do not cause any raceconditions, damaging the state of the session. Other caching protocolslike MESI protocol may also be used to achieve similar results. When asession entry is cached in a processor complex, and another processorcomplex needs that entry, this entry is transferred to the new processorwith exclusive access or appropriate caching state based on thealgorithm. The session entry may also get written to the global sessionmemory in certain cases. The TCP/IP processor also includes a TCP statemachine, block 2322, which is used to walk through the TCP states forthe connection being operated on. This state machine receives the stateinformation stored in the session entry along with the appropriatefields affecting the state from the newly received packet. This allowsthe state machine to generate the next state if there is a statetransition and the information is updated in the session table entry.The TCP/IP processor also includes a frame controller/out of ordermanager block, 2318, that is used to extract the frame information andperform operations for out of order packet execution. This block couldalso include an RDMA mechanism such as that shown at 2417 of FIG. 24,but used for non-storage data transfers. One of ordinary skill in theart can also, with the teaching of this patent, implement an RDMAmechanism elsewhere on the TCP/IP processor. This architecture createsan upper layer framing mechanism which may use packet CRC as framing keyor other keys that is used by the programmable frame controller toextract the embedded PDUs even when the packets arrive out of order andallow them to be directed to the end buffer destination. This unitinteracts with the session database to handle out of order arrivalinformation which is recorded so that once the intermediate segmentsarrive, the retransmissions are avoided. Once the packet has beenprocessed through the TCP/IP processor, it is delivered for operation tothe storage engine, if the packet belongs to a storage data transfer andthe specific implementation includes a storage engine, otherwise thepacket is passed on to the host processor interface or the storageflow/RDMA controller of block 1708 for processing and for DMA to the endbuffer destination. The packet may be transferred to the packetprocessor block as well for any additional processing on the packet.This may include application and customer specific application code thatcan be executed on the packet before or after the processing by theTCP/IP processor and the storage processor. Data transfer from the hostto the output media interface would also go through the TCP/IP processorto form the appropriate headers to be created around the data and alsoperform the appropriate data segmentation, working with the framecontroller and/or the storage processor as well as to update the sessionstate. This data may be retrieved as a result of host command orreceived network packet scheduled by the scheduler to the packetprocessor for operation. The internal bus structures and functionalblock interconnections may be different than illustrated forperformance, die cost requirements and the like. For example, HostController Interface 2301, Scheduler Interface 2307 and MemoryController Interface 2323 may be part of a bus controller that allowstransfer of data packets or state information or commands, or acombination thereof, to or from a scheduler or storage flow/RDMAcontroller or host or session controller or other resources such as,without limitation, security processor, or media interface units, hostinterface, scheduler, classification processor, packet buffers orcontroller processor, or any combination of the foregoing.

FIG. 24 illustrates the IP storage processor engine of FIG. 22 in moredetail. The storage engine. is a programmable engine with an instructionset that is geared towards IP based storage along with, usually, anormal RISC-like packet processing instruction set. The IP storageprocessor engine contains block 2411, to perform CRC operations. Thisblock allows CRC generation and verification. The incoming packet withIP storage is transferred from the TCP/IP engine through DMA, blocks2402 and 2408, into the data memory (a data RAM is an example of suchmemory), block 2409. When the implementation does not include TCP/IPengine or packet processor engine or a combination thereof, the packetmay be received from the scheduler directly for example. The TCP sessiondatabase information related to the connection can be retrieved from thelocal session cache as needed or can also be received with the packetfrom the TCP/IP engine The storage PDU is provided to the PDU classifierengine, block 2418, which classifies the PDU into the appropriatecommand, which is then used to invoke the appropriate storage commandexecution engine, block 2412. The command execution can be accomplishedusing the RISC, or equivalent, instruction set or using a dedicatedhardware engine. The command execution engines perform the commandreceived in the PDU. The received PDU may contain read command data, orR2T for a pending write command or other commands required by the IPstorage protocol. These engines retrieve the write data from the hostinterface or direct the read data to the destination buffer. The storagesession database entry is cached, in what can be viewed as a localmemory, block 2420, locally for the recent or frequent connectionsserved by the processor. The command execution engines execute thecommands and make the storage database entry updates working with thestorage state machine, block 2422, and the session manager, block 2421.The connection ID is used to identify the session, and if the session isnot present in the cache, then it is retrieved from the global sessionmemory 1704 of FIG. 17 by the storage session look-up engine, block2419. For data transfer from the initiator to target, the processor usesthe segmentation controller, block 2413, to segment the data units intosegments as per various network constraints like path MTU and the like.The segmentation controller attempts to ensure that the outgoing PDUsare optimal size for the connection. If the data transfer requested islarger than the maximum effective segment size, then the segmentationcontroller packs the data into multiple packets and works with thesequence manager, block 2415, to assign the sequence numbersappropriately. The segmentation controller 2413 may also be implementedwithin the TCP/IP processor of FIG. 23. That is, the segmentationcontroller may be part of the sequence/window operations manager 2315 ofFIG. 23 when this processor is used for TCP/IP operations and notstorage operations. One of ordinary skill in the art can easily suggestalternate embodiments for including the segmentation controller in theTCP/IP processor using the teachings of this patent. The storageprocessor of FIG. 24 (or the TCP/IP processor of FIG. 23) can alsoinclude an RDMA engine that interprets the remote direct memory accessinstructions received in the PDUs for storage or network data transfersthat are implemented using this RDMA mechanism. In FIG. 24, for example,this is RDMA engine 2417. In the TCP/IP processor of FIG. 23 an RDMAengine could be part of the frame controller and out of order manager2318, or other suitable component. If both ends of the connection agreeto the RDMA mode of data transfer, then the RDMA engine is utilized toschedule the data transfers between the target and initiator withoutsubstantial host intervention. The RDMA transfer state is maintained ina session database entry. This block creates the RDMA headers to belayered around the data, and is also used to extract these headers fromthe received packets that are received on RDMA enabled connections. TheRDMA engine works with the storage flow/RDMA controller, 1708, and thehost interface controller, 1710, by passing the messages/instructionsand performs the large block data transfers without substantial hostintervention. The RDMA engine of the storage flow/RDMA controller block,1708, of the IP processor performs protection checks for the operationsrequested and also provides conversion from the RDMA region identifiersto the physical or virtual address in the host space. This functionalitymay also be provided by RDMA engine, block 2417, of the storage engineof the SAN packet processor based on the implementation chosen. Thedistribution of the RDMA capability between 2417 and 1708 and othersimilar engines is an implementation choice that one with ordinary skillin the art will be able to do with the teachings of this patent.Outgoing data is packaged into standards based PDU by the PDU creator,block 2425. The PDU formatting may also be accomplished by using thepacket processing instructions. The storage engine of FIG. 24 works withthe TCP/IP engine of FIG. 23 and the packet processor engine of FIG. 17to perform the IP storage operations involving data and commandtransfers in both directions i.e. from the initiator to target and thetarget to the host and vice versa. That is, the Host controllerInterface 2401, 2407 store and retrieve commands or data or acombination thereof to or from the host processor. These interfaces maybe directly connected to the host or may be connected through anintermediate connection. Though shown as two apparatus, interfaces 2401and 2407 could be implemented as a single apparatus. The flow of datathrough these blocks would be different based on the direction of thetransfer. For instance, when command or data is being sent from the hostto the target, the storage processing engines will be invoked first toformat the PDU and then this PDU is passed on to the TCP processor topackage the PDU in a valid TCP/IP segment. However, a received packetwill go through the TCP/IP engine before being scheduled for the storageprocessor engine. The internal bus structures and functional blockinterconnections may be different than illustrated for performance, diecost requirements, and the like. For example, and similarly to FIG. 23,Host Controller Interface 2401, 2407 and Memory Controller Interface2423 may be part of a bus controller that allows transfer of datapackets or state information or commands, or a combination thereof, toor from a scheduler or host or storage flow/RDMA controller or sessioncontroller or other resources such as, without limitation, securityprocessor, or media interface units, host interface, scheduler,classification processor, packet buffers or controller processor, or anycombination of the foregoing.

In applications in which storage is done on a chip not including theTCP/IP processor of FIG. 23 by, as one example, an IP Storage processorsuch as an iSCSI processor of FIG. 24, the TCP/IP Interface 2406 wouldfunction as an interface to a scheduler for scheduling IP storage packetprocessing by the IP Storage processor. Similar variations are wellwithin the knowledge of one of ordinary skill in the art, viewing thedisclosure of this patent.

FIG. 25 illustrates the output queue controller block 1712 of FIG. 17 inmore detail. This block receives the packets that need to be sent on tothe network media independent interface 1601 of FIG. 16. The packets maybe tagged to indicate if they need to be encrypted before being sentout. The controller queues the packets that need to be secured to thesecurity engine through the queue 2511 and security engine interface2510. The encrypted packets are received from the security engine andare queued in block 2509, to be sent to their destination. The outputqueue controller may assign packets onto their respective quality ofservice (QOS) queues, if such a mechanism is supported. The programmablepacket priority selector, block 2504, selects the next packet to be sentand schedules the packet for the appropriate port, Port1 . . . PortN.The media controller block 1601 associated with the port accepts thepackets and sends them to their destination.

FIG. 26 illustrates the storage flow controller/RDMA controller block,shown generally at 1708 of FIG. 17, in more detail. The storage flow andRDMA controller block provides the functionality necessary for the hostto queue the commands (storage or RDMA or sockets direct or acombination thereof) to this processor, which then takes these commandsand executes them, interrupting the host processor primarily on commandtermination. The command queues, new and active, blocks 2611 and 2610,and completion queue, block 2612, can be partially on chip and partiallyin a host memory region or memory associated with the IP processor, fromwhich the commands are fetched or the completion status deposited. TheRDMA engine, block 2602, provides various capabilities necessary forenabling remote direct memory access. It has tables, like RDMA look-uptable 2608, that include information like RDMA region and the accesskeys, and virtual address translation functionality. The RDMA engineinside this block 2602 performs the data transfer and interprets thereceived RDMA commands to perform the transaction if allowed. Thestorage flow controller also keeps track of the state of the progress ofvarious commands that have been scheduled as the data transfer happensbetween the target and the initiator. The storage flow controllerschedules the commands for execution and also provides the commandcompletion information to the host drivers. The storage flow controllerprovides command queues where new requests from the host are deposited,as well as active commands are held in the active commands queue. Thecommand scheduler of block 2601, assigns new commands, that are receivedwhich are for targets for which no connections exist, to the schedulerfor initiating a new connection. The scheduler 1702, uses the controlplane processor shown generally at 1711 of FIG. 17 to do the connectionestablishment at which point the connection entry is moved to thesession cache, shown generally in FIGS. 15 and 1704 in FIG. 17, and thestate controller in the storage flow controller block 2601 moves the newcommand to active commands and associates the command to the appropriateconnection. The active commands, in block 2610, are retrieved and sentto the scheduler, block 1702 for operation by the packet processors. Theupdate to the command status is provided back to the flow controllerwhich then stores it in the command state tables, blocks 2607 andaccessed through block 2603. The sequencer of 2601 applies aprogrammable priority for command scheduling and thus selects the nextcommand to be scheduled from the active commands and new commands. Theflow controller also includes a new requests queue for incomingcommands, block 2613. The new requests are transferred to the activecommand queue once the appropriate processing and buffer reservationsare done on the host by the host driver. As the commands are beingscheduled for execution, the state controller 2601 initiates datapre-fetch by host data pre-fetch manager, block 2617, from the hostmemory using the DMA engine of the host interface block 2707, hencekeeping the data ready to be provided to the packet processor complexwhen the command is being executed. The output queue controller, block2616, enables the data transfer, working with the host controllerinterface, block 2614. The storage flow/RDMA controller maintains atarget-initiator table, block 2609, that associates thetarget/initiators that have been resolved and connections establishedfor fast look-ups and for associating commands to active connections.The command sequencer may also work with the RDMA engine 2602, if thecommands being executed are RDMA commands or if the storage transferswere negotiated to be done through the RDMA mechanism at the connectioninitiation. The RDMA engine 2602, as discussed above, providesfunctionality to accept multiple RDMA regions, access control keys andthe virtual address translation pointers. The host application (whichmay be a user application or an OS kernel function, storage ornon-storage such as downloading web pages, video files, or the like)registers a memory region that it wishes to use in RDMA transactionswith the disclosed processor through the services provided by theassociated host driver. Once this is done, the host applicationcommunicates this information to its peer on a remote end. Now, theremote machine or the host can execute RDMA commands, which are servedby the RDMA blocks on both ends without requiring substantial hostintervention. The RDMA transfers may include operations like read from aregion, a certain number of bytes with a specific offset or a write withsimilar attributes. The RDMA mechanism may also include sendfunctionality which would be useful in creating communication pipesbetween two end nodes. These features are useful in clusteringapplications where large amounts of data transfer is required betweenbuffers of two applications running on servers in a cluster, or morelikely, on servers in two different clusters of servers, or such otherclustered systems. The storage data transfer may also be accomplishedusing the RDMA mechanism, since it allows large blocks of data transferswithout substantial host intervention. The hosts on both ends getinitially involved to agree on doing the RDMA transfers and allocatingmemory regions and permissions through access control keys that getshared. Then the data transfer between the two nodes can continuewithout host processor intervention, as long as the available bufferspace and buffer transfer credits are maintained by the two end nodes.The storage data transfer protocols would run on top of RDMA, byagreeing to use RDMA protocol and enabling it on both ends. The storageflow controller and RDMA controller of FIG. 26 can then perform thestorage command execution and the data transfer using RDMA commands. Asthe expected data transfers are completed the storage command completionstatus is communicated to the host using the completion queue 2612. Theincoming data packets arriving from the network are processed by thepacket processor complex of FIG. 17 and then the PDU is extracted andpresented to the flow controller OF FIG. 26 in case of storage/RDMA datapackets. These are then assigned to the incoming queue block 2604, andtransferred to the end destination buffers by looking up the memorydescriptors of the receiving buffers and then performing the DMA usingthe DMA engine inside the host interface block 2707. The RDMA commandsmay also go through protection key look-up and address translation asper the RDMA initialization.

The foregoing may also be considered a part of an RDMA capability or anRDMA mechanism or an RDMA function.

FIG. 27 illustrates host interface controller 1710 of FIG. 17 in moredetail. The host interface block includes a host bus interfacecontroller, block 2709, which provides the physical interface to thehost bus. The host interface block may be implemented as a fabricinterface or media independent interface when embodied in a switch or agateway or similar configuration depending on the system architectureand may provide virtual output queuing and/or other quality of servicefeatures. The transaction controller portion of block 2708, executesvarious bus transactions and maintains their status and takes requestedtransactions to completion. The host command unit, block 2710, includeshost bus configuration registers and one or more command interpreters toexecute the commands being delivered by the host. The host driverprovides these commands to this processor over Host Output QueueInterface 2703. The commands serve various functions like setting upconfiguration registers, scheduling DMA transfers, setting up DMAregions and permissions if needed, setup session entries, retrievesession database, configure RDMA engines and the like. The storage andother commands may also be transferred using this interface forexecution by the IP processor.

FIG. 28 illustrates the security engine 1705 of FIG. 17 in more detail.The security engine illustrated provides authentication and encryptionand decryption services like those required by standards like IPSEC forexample. The services offered by the security engine may includemultiple authentication and security algorithms. The security engine maybe on board the processor or may be part of a separate silicon chip asindicated earlier. An external security engine providing IP securityservices would be situated in a similar position in the data flow, asone of the first stages of packet processing for incoming packets and asone of the last stages for the outgoing packet. The security engineillustrated provides advanced encryption standard (AES) based encryptionand decryption services, which are very hardware performance efficientalgorithms adopted as security standards. This block could also provideother security capabilities like DES, 3DES, as an example. The supportedalgorithms and features for security and authentication are driven fromthe silicon cost and development cost. The algorithms chosen would alsobe those required by the IP storage standards. The authenticationengine, block 2803, is illustrated to include the SHA-1 algorithm as oneexample of useable algorithms. This block provides message digest andauthentication capabilities as specified in the IP security standards.The data flows through these blocks when security and messageauthentication services are required. The clear packets on their way outto the target are encrypted and are then authenticated if required usingthe appropriate engines. The secure packets received go through the samesteps in reverse order. The secure packet is authenticated and thendecrypted using the engines 2803, 2804 of this block. The securityengine also maintains the security associations in a security contextmemory, block 2809, that are established for the connections. Thesecurity associations (may include secure session index, security keys,algorithms used, current state of session and the like) are used toperform the message authentication and the encryption/decryptionservices. It is possible to use the message authentication service andthe encryption/decryption services independent of each other.

FIG. 29 illustrates the session cache and memory controller complex seengenerally at 1704 of FIG. 17 in more detail. The memory complex includesa cache/memory architecture for the TCP/IP session database calledsession/global session memory or session cache in this patent,implemented as a cache or memory or a combination thereof. The sessioncache look-up engine, block 2904, provides the functionality to look-upa specific session cache entry. This look-up block creates a hash indexout of the fields provided or is able to accept a hash key and looks-upthe session cache entry. If there is no tag match in the cache arraywith the hash index, the look-up block uses this key to find the sessionentry from the external memory and replaces the current session cacheentry with that session entry. It provides the session entry fields tothe requesting packet processor complex. The cache entries that arepresent in the local processor complex cache are marked shared in theglobal cache. Thus when any processor requests this cache entry, it istransferred to the global cache and the requesting processor and markedas such in the global cache. The session memory controller is alsoresponsible to move the evicted local session cache entries into theglobal cache inside this block. Thus only the latest session state isavailable at any time to any requesters for the session entry. If thesession cache is full, a new entry may cause the least recently usedentry to be evicted to the external memory. The session memory may besingle way or multi-way cache or a hash indexed memory or a combinationthereof, depending on the silicon real estate available in a givenprocess technology. The use of a cache for storing the session databaseentry is unique, in that in networking applications for network switchesor routers, generally there is not much locality of reference propertiesavailable between packets, and hence use of cache may not provide muchperformance improvement due to cache misses. However, the storagetransactions are longer duration transactions between the two endsystems and may exchange large amounts of data. In this scenario orcases where a large amount of data transfer occurs between two nodes,like in clustering or media servers or the like a cache based sessionmemory architecture will achieve significant performance benefit fromreducing the enormous data transfers from the off chip memories. Thesize of the session cache is a function of the available silicon diearea and can have an impact on performance based on the trade-off. Thememory controller block also provides services to other blocks that needto store packets, packet fragments or any other operating data inmemory. The memory interface provides single or multiple external memorycontrollers, block 2901, depending on the expected data bandwidth thatneeds to be supported. This can be a double data rate controller orcontroller for DRAM or SRAM or RDRAM or other dynamic or static RAM orcombination thereof. The figure illustrates multi-controllers howeverthe number is variable depending on the necessary bandwidth and thecosts. The memory complex may also provide timer functionality for usein retransmission time out for sessions that queue themselves on theretransmission queues maintained by the session database memory block.

FIG. 30 illustrates the data structures details for the classificationengine. This is one way of organizing the data structures for theclassification engine. The classification database is illustrated as atree structure, block 3001, with nodes, block 3003, in the tree and theactions, block 3008, associated with those nodes allow theclassification engine to walk down the tree making comparisons for thespecific node values. The node values and the fields they represent areprogrammable. The action field is extracted when a field matches aspecific node value. The action item defines the next step, which mayinclude extracting and comparing a new field, performing otheroperations like ALU operations on specific data fields associated withthis node-value pair, or may indicate a terminal node, at which pointthe classification of the specific packet is complete. This datastructure is used by the classification engine to classify the packetsthat it receives from the packet scheduler. The action items that areretrieved with the value matches, while iterating different fields ofthe packet, are used by the results compiler to create a classificationtag, which is attached to the packet, generally before the packetheaders. The classification tag is then used as a reference by the restof the processor to decide on the actions that need to be taken based onthe classification results. The classifier with its programmablecharacteristics allows the classification tree structure to be changedin-system and allow the processor to be used in systems that havedifferent classification needs. The classification engine also allowscreation of storage/network policies that can be programmed as part ofthe classification tree-node-value-action structures and provide a verypowerful capability in the IP based storage systems. The policies wouldenhance the management of the systems that use this processor and allowenforcement capabilities when certain policies or rules are met orviolated. The classification engine allows expansion of theclassification database through external components, when that isrequired by the specific system constraints. The number of trees andnodes are decided based on the silicon area and performance tradeoffs.The data structure elements are maintained in various blocks of theclassification engine and are used by the classification sequencer todirect the packet classification through the structures. Theclassification data structures may require more or less fields thanthose indicated depending on the target solution. Thus the corefunctionality of classification may be achieved with fewer componentsand structures without departing from the basic architecture. Theclassification process walks through the trees and the nodes asprogrammed. A specific node action may cause a new tree to be used forthe remaining fields for classification. Thus, the classificationprocess starts at the tree root and progress through the nodes until itreaches the leaf node.

FIG. 31 illustrates a read operation between an initiator and target.The initiator sends a READ command request, block 3101, to the target tostart the transaction. This is an application layer request which ismapped to specific SCSI protocol command which is than transported as anREAD protocol data unit, block 3102, in an IP based storage network. Thetarget prepares the data that is requested, block 3103 and provides readresponse PDUs, block 3105, segmented to meet the maximum transfer unitlimits. The initiator then retrieves the data, block 3016, from the IPpackets and is then stored in the read buffers allocated for thisoperation. Once all the data has been transferred the target respondswith command completion and sense status, block 3107. The initiator thenretires the command once the full transfer is complete, block 3109. Ifthere were any errors at the target and the command is being aborted forany reason, then a recovery procedure may be initiated separately by theinitiator. This transaction is a standard SCSI READ transaction with thedata transport over IP based storage protocol like iSCSI as the PDUs ofthat protocol.

FIG. 32 illustrates the data flow inside the IP processor of thisinvention for one of the received READ PDUs of the transactionillustrated in FIG. 31. The internal data flow is shown for the readdata PDU received by the IP processor on the initiator end. This figureillustrates various stage of operation that a packet goes through. Thestages can be considered as pipeline stages through which the packetstraverse. The number of pipe stages traversed depends on the type of thepacket received. The figure illustrates the pipe stages for a packetreceived on an established connection. The packet traverses through thefollowing major pipe stages:

1. Receive Pipe Stage of block 3201, with major steps illustrated inblock 3207: Packet is received by the media access controller. Thepacket is detected, the preamble/trailers removed and a packet extractedwith the layer2 header and the payload. This is the stage where theLayer2 validation occurs for the intended recipient as well as any errordetection. There may be quality of service checks applied as per thepolicies established. Once the packet validation is clear the packet isqueued to the input queue.

2. Security Pipe Stage of block 3202, with major steps illustrated inblock 3208. The packet is moved from the input queue to theclassification engine, where a quick determination for securityprocessing is made and if the packet needs to go through securityprocessing, it enters the security pipe stage. If the packet is receivedin clear text and does not need authentication, then the security pipestage is skipped. The security pipe stage may also be omitted if thesecurity engine is not integrated with the IP processor. The packet goesthrough various stages of security engine where first the securityassociation for this connection is retrieved from memory, and the packetis authenticated using the message authentication algorithm selected.The packet is then decrypted using the security keys that have beenestablished for the session. Once the packet is in clear text, it isqueued back to the input queue controller.

3. Classification Pipe Stage of block 3203, with major steps illustratedin block 3209. The scheduler retrieves the clear packet from the inputqueue and schedules the packet for classification. The classificationengine performs various tasks like extracting the relevant fields fromthe packet for layer 3 and higher layer classification, identifiesTCP/IP/storage protocols and the like and creates those classificationtags and may also take actions like rejecting the packet or tagging thepacket for bypass depending on the policies programmed in theclassification engine. The classification engine may also tag the packetwith the session or the flow to which it belongs along with marking thepacket header and payload for ease of extraction. Some of the taskslisted may be or may not be performed and other tasks may be performeddepending on the programming of the classification engine. As theclassification is done, the classification tag is added to the packetand packet is queued for the scheduler to process.

4. Schedule Pipe Stage of block 3204, with major steps illustrated inblock 3210. The classified packet is retrieved from the classificationengine queue and stored in the scheduler for it to be processed. Thescheduler performs the hash of the source and destination fields fromthe packet header to identify the flow to which the packet belongs, ifnot done by the classifier. Once the flow identification is done thepacket is assigned to an execution resource queue based on the flowdependency. As the resource becomes available to accept a new packet,the next packet in the queue is assigned for execution to that resource.

5. Execution Pipe Stage of block 3205, with major steps illustrated inblock 3211. The packet enters the execution pipe stage when the resourceto execute this packet becomes available. The packet is transferred tothe packet processor complex that is supposed to execute the packet. Theprocessor looks at the classification tag attached to the packet todecide the processing steps required for the packet. If this is an IPbased storage packet, then the session database entry for this sessionis retrieved. The database access may not be required if the localsession cache already holds the session entry. If the packet assignmentwas done based on the flow, then the session entry may not need to beretrieved from the global session memory. The packet processor thenstarts the TCP engine/the storage engines to perform their operations.The TCP engine performs various TCP checks including checksum, sequencenumber checks, framing checks with necessary CRC operations, and TCPstate update. Then the storage PDU is extracted and assigned to thestorage engine for execution. The storage engine interprets the commandin the PDU and in this particular case identifies it to be a readresponse for an active session. It than verifies the payload integrityand the sequence integrity and then updates the storage flow state inthe session database entry. The memory descriptor of the destinationbuffer is also retrieved from the session data base entry and theextracted PDU payload is queued to the storage flow/RDMA controller andthe host interface block for them to DMA the data to the final bufferdestination. The data may be delivered to the flow controller with thememory descriptor and the command/operation to perform. In this casedeposit the data for this active read command. The storage flowcontroller updates its active command database. The execution engineindicates to the scheduler the packet has been retired and the packetprocessor complex is ready to receive its next command.

6. DMA Pipe Stage of block 3206, with major steps illustrated in block3212. Once the storage flow controller makes the appropriateverification of the Memory descriptor, the command and the flow state,it passes the data block to the host DMA engine for transfer to the hostmemory. The DMA engine may perform priority based queuing, if such QOSmechanism is programmed or implemented. The data is transferred to thehost memory location through DMA. If this is the last operation of thecommand, then the command execution completion is indicated to the hostdriver. If this is the last operation for a command and the command hasbeen queued to the completion queue, the resources allocated for thecommand are released to accept new command. The command statistics maybe collected and transferred with the completion status as may berequired for performance analysis, policy management or other networkmanagement or statistical purposes.

FIG. 33 illustrates write command operation between an initiator and atarget. The Initiator sends a WRITE command, block 3301, to the targetto start the transaction. This command is transported as a WRITE PDU,block 3302, on the IP storage network. The receiver queues the receivedcommand in the new request queue. Once the old commands in operation arecompleted, block 3304, the receiver allocates the resources to acceptthe WRITE data corresponding to the command, block 3305. At this stagethe receiver issues a ready to transfer (R2T) PDU, block 3306, to theinitiator, with indication of the amount of data it is willing toreceive and from which locations. The initiator interprets the fields ofthe R2T requests and sends the data packets, block 3307, to the receiveras per the received R2T. This sequence of exchange between the initiatorand target continues until the command is terminated. A successfulcommand completion or an error condition is communicated to theinitiator by the target as a response PDU, which then terminates thecommand. The initiator may be required to start a recovery process incase of an error. This is not shown in the exchange of the FIG. 33.

FIG. 34 illustrates the data flow inside the IP processor of thisinvention for one of the R2T PDUs and the following write data of thewrite transaction illustrated in FIG. 33. The initiator receives the R2Tpacket through its network media interface. The packet passes throughall the stages, blocks 3401, 3402, 3403, and 3404 with detailed majorsteps in corresponding blocks 3415, 3416, 3409 and 3410, similar to theREAD PDU in FIG. 32 including Receive, Security, Classification,Schedule, and Execution. Security processing is not illustrated in thisfigure. Following these stages the R2T triggers the write data fetchusing the DMA stage shown in FIG. 34, blocks 3405 and 3411. The writedata is then segmented and put in TCP/IP packets through the executionstage, blocks 3406 and 3412. The TCP and storage session DB entries areupdated for the WRITE command with the data transferred in response tothe R2T. The packet is then queued to the output queue controller.Depending on the security agreement for the connection, the packet mayenter the security pipe stage, block 3407 and 3413. Once the packet hasbeen encrypted and message authentication codes generated, the packet isqueued to the network media interface for the transmission to thedestination. During this stage, block 3408 and 3414 the packet isencapsulated in the Layer 2 headers, if not already done so by thepacket processor and is transmitted. The steps followed in each stage ofthe pipeline are similar to that of the READ PDU pipe stages above, withadditional stages for the write data packet stage, which is illustratedin this figure. The specific operations performed in each stage dependon the type of the command, the state of the session, the command stateand various other configurations for policies that may be setup.

FIG. 35 illustrates the READ data transfer using RDMA mechanism betweenand initiator and target. The initiator and target register the RDMAbuffers before initiating the RDMA data transfer, blocks 3501, 3502, and3503. The initiator issues a READ command, block 3510, with the RDMAbuffer as the expected recipient. This command is transported to thetarget, block 3511. The target prepares the data to be read, block 3504,and then performs the RDMA write operations, block 3505 to directlydeposit the read data into the RDMA buffers at the initiator without thehost intervention. The operation completion is indicated using thecommand completion response.

FIG. 36 illustrates the internal architecture data flow for the RDMAWrite packet implementing the READ command flow. The RDMA write packetalso follows the same pipe stages as any other valid data packet that isreceived on the network interface. This packet goes through Layer 2processing in the receive pipe stage, blocks 3601 and 3607, from whereit is queued for scheduler to detect the need for security processing.If the packet needs to be decrypted or authenticated, it enters thesecurity pipe stage, blocks 3602 and 3608. The decrypted packet is thenscheduled to the classification engine for it to perform theclassification tasks that have been programmed, blocks 3603 and 3609.Once classification is completed, the tagged packet enters the schedulepipe stage, blocks 3604 and 3610, where the scheduler assigns thispacket to a resource specific queue dependent on flow based scheduling.When the intended resource is ready to execute this packet, it istransferred to that packet processor complex, blocks 3605 and 3611,where all the TCP/IP verification, checks, and state updates are madeand the PDU is extracted. Then the storage engine identifies the PDU asbelonging to a storage flow for storage PDUs implemented using RDMA andinterprets the RDMA command. In this case it is RDMA write to a specificRDMA buffer. This data is extracted and passed on to the storageflow/RDMA controller block which performs the RDMA region translationand protection checks and the packet is queued for DMA through the hostinterface, blocks 3606 and 3612. Once the packet has completed operationthrough the packet processor complex, the scheduler is informed and thepacket is retired from the states carried in the scheduler. Once in theDMA stage, the RDMA data transfer is completed and if this is the lastdata transfer that completes the storage command execution, that commandis retired and assigned to the command completion queue.

FIG. 37 illustrates the storage write command execution using RDMA Readoperations. The initiator and target first register their RDMA bufferswith their RDMA controllers and then also advertise the buffers to theirpeer. Then the initiator issues a write command, block 3701, to thetarget, where it is transported using the IP storage PDU. The recipientexecutes the write command, by first allocating the RDMA buffer toreceive the write and then requesting an RDMA read to the initiator,blocks 3705, and 3706. The data to be written from the initiator is thenprovided as an RDMA read response packet, blocks 3707 and 3708. Thereceiver deposits the packet directly to the RDMA buffer without anyhost interaction. If the read request was for data larger than thesegment size, then multiple READ response PDUs would be sent by theinitiator in response to the READ request. Once the data transfer iscomplete the completion status is transported to the initiator and thecommand completion is indicated to the host.

FIG. 38 illustrates the data flow of an RDMA Read request and theresulting write data transfer for one section of the flow transactionillustrated in FIG. 37. The data flow is very similar to the write dataflow illustrated in FIG. 34. The RDMA read request packet flows throughvarious processing pipe stages including: receive, classify, schedule,and execution, blocks 3801, 3802, 3803, 3804, 3815, 3816, 3809 and 3810.Once this request is executed, it generates the RDMA read responsepacket. The RDMA response is generated by first doing the DMA, blocks3805 and 3811, of the requested data from the system memory, and thencreating segments and packets through the execution stage, blocks 3806and 3812. The appropriate session database entries are updated and thedata packets go to the security stage, if necessary, blocks 3807 and3813. The secure or clear packets are then queued to the transmit stage,block 3808 and 3814, which performs the appropriate layer 2 updates andtransmits the packet to the target.

FIG. 39 illustrates an initiator command flow for the storage commandsinitiated from the initiator in more details. As illustrated followingare some of the major steps that a command follows:

1. Host driver queues the command in processor command queue in thestorage flow/RDMA controller;

2. Host is informed if the command is successfully scheduled foroperation and to reserve the resources;

3. The storage flow/RDMA controller schedules the command for operationto the packet scheduler, if the connection to the target is established.Otherwise the controller initiates the target session initiation andonce session is established the command is scheduled to the packetscheduler;

4. The scheduler assigns the command to one of the SAN packet processorsthat is ready to accept this command;

5. The processor complex sends a request to the session controller forthe session entry;

6. The session entry is provided to the packet processor complex;

7. The packet processor forms a packet to carry the command as a PDU andis scheduled to the output queue; and

8. The command PDU is given to the network media interface, which sendsit to the target.

This is the high level flow primarily followed by most commands from theinitiator to the target when the connection has been established betweenan initiator and a target.

FIG. 40 illustrates read packet data flow in more detail. Here the readcommand is initially send using a flow similar to that illustrated inFIG. 39 from the initiator to the target. The target sends the readresponse PDU to the initiator which follows the flow illustrated in FIG.40. As illustrated the read data packet passes through following majorsteps:

1. Input packet is received from the network media interface block; 2.Packet scheduler retrieves the packet from the input queue; 3. Packet isscheduled for classification; 4. Classified packet returns from theclassifier with a classification tag; 5. Based on the classification andflow based resource allocation, the packet is assigned to a packetprocessor complex which operates on the packet; 6. Packet processorcomplex looks-up session entry in the session cache (if not presentlocally); 7. Session cache entry is returned to the packet processorcomplex; 8. Packet processor complex performs the TCP/IP operations/IPstorage operations and extracts the read data in the payload. The readdata with appropriate destination tags like MDL (memory descriptor list)is provided to the host interface output controller; and 9. The host DMAengine transfers the read data to the system buffer memory.

Some of these steps are provided in more details in FIG. 32, where asecure packet flow is represented, where as the FIG. 40 represents aclear text read packet flow. This flow and other flows illustrated inthis patent are applicable to storage and non-storage data transfers byusing appropriate resources of the disclosed processor, that a personwith ordinary skill in the art will be able to do with the teachings ofthis patent.

FIG. 41 illustrates the write data flow in more details. The writecommand follows the flow similar to that in FIG. 39. The initiator sendsthe write command to the target. The target responds to the initiatorwith a ready to transfer (R2T) PDU which indicates to the initiator thatthe target is ready to receive the specified amount of data. Theinitiator then sends the requested data to the target. FIG. 41illustrates the R2T followed by the requested write data packet from theinitiator to the target. The major steps followed in this flow are asfollows:

1. Input packet is received from the network media interface block; 2.Packet scheduler retrieves the packet from the input queue; 3. Packet isscheduled for classification; 4. Classified packet returns from theclassifier with a classification tag; a. Depending on the classificationand flow based resource allocation, the packet is assigned to a packetprocessor complex which operates on the packet; 5. Packet processorcomplex looks-up session entry in the session cache (if not presentlocally); 6. Session cache entry is returned to the packet processorcomplex; 7. The packet processor determines the R2T PDU and requests thewrite data with a request to the storage flow/RDMA Controller; 8. Theflow controller starts the DMA to the host interface; 9. Host interfaceperforms the DMA and returns the data to the host input queue; 10. Thepacket processor complex receives the data from the host input queue;11. The packet processor complex forms a valid PDU and packet around thedata, updates the appropriate session entry and transfers the packet tothe output queue; and 12. The packet is transferred to the outputnetwork media interface block which transmits the data packet to thedestination. The flow in FIG. 41 illustrates clear text data transfer.If the data transfer needs to be secure, the flow is similar to thatillustrated in FIG. 43, where the output data packet is routed throughthe secure packet as illustrated by arrows labeled 11 a and 11 b. Theinput R2T packet, if secure would also be routed through the securityengine (this is not illustrated in the figure).

FIG. 42 illustrates the read packet flow when the packet is in ciphertext or is secure. This flow is illustrated in more details in FIG. 32with its associated description earlier. The primary difference betweenthe secure read flow and the clear read flow is that the packet isinitially classified as secure packet by the classifier, and hence isrouted to the security engine. These steps are illustrated by arrowslabeled 2 a, 2 b, and 2 c. The security engine decrypts the packet andperforms the message authentication, and transfers the clear packet tothe input queue for further processing as illustrated by arrow labeled 2d. The clear packet is then retrieved by the scheduler and provided tothe classification engine as illustrated by arrows labeled 2 e and 3 inFIG. 42. The rest of the steps and operations are the same as that inFIG. 40, described above.

FIG. 44 illustrates the RDMA buffer advertisement flow. This flow isillustrated to be very similar to any other storage command flow asillustrated in the FIG. 39. The detailed actions taken in the majorsteps are different depending on the command. For RDMA bufferadvertisement and registration, the RDMA region id is created andrecorded along with the address translation mechanism for this region isrecorded. The RDMA registration also includes the protection key for theaccess control and may include other fields necessary for RDMA transfer.The steps to create the packet for the command are similar to those ofFIG. 39.

FIG. 45 illustrates the RDMA write flow in more details. The RDMA writesappear like normal read PDUs to the initiator receiving the RDMA write.The RDMA write packet follows the same major flow steps as a read PDUillustrated in FIG. 40. The RDMA transfer involves the RDMA addresstranslation and region access control key checks, and updating the RDMAdatabase entry, beside the other session entries. The major flow stepsare the same as the regular Read response PDU.

FIG. 46 illustrates the RDMA Read data flow in more details. Thisdiagram illustrates the RDMA read request being received by theinitiator from the target and the RDMA Read data being written out fromthe initiator to the target. This flow is very similar to the R2Tresponse followed by the storage write command. In this flow the storagewrite command is accomplished using RDMA Read. The major steps that thepacket follows are primarily the same as the R2T/write data flowillustrated in FIG. 41.

FIG. 47 illustrates the major steps of session creation flow. Thisfigure illustrates the use of the control plane processor for this slowpath operation required at the session initiation between an initiatorand a target. This functionality is possible to implement through thepacket processor complex. However, it is illustrated here as beingimplemented using the control plane processor. Both approaches areacceptable. Following are the major steps during session creation:

1. The command is scheduled by the host driver; 2. The host driver isinformed that the command is scheduled and any control informationrequired by the host is passed; 3. The storage flow/RDMA controllerdetects a request to send the command to a target for which a session isnot existing, and hence it passes the request to the control planeprocessor to establish the transport session; 4. Control plane processorsends a TCP SYN packet to the output queue; 5. The SYN packet istransmitted to the network media interface from which is transmitted tothe destination; 6. The destination, after receiving the SYN packet,responds with the SYN-ACK response, which packet is queued in the inputqueue on receipt from the network media interface; 7. The packet isretrieved by the packet scheduler; 8. The packet is passed to theclassification engine; 9. The tagged classified packet is returned tothe scheduler; 10. The scheduler, based on the classification, forwardsthis packet to control plane processor; 11. The processor then respondswith an ACK packet to the output queue; 12. The packet is thentransmitted to the end destination thus finishing the sessionestablishment handshake; and 13. Once the session is established, thisstate is provided to the storage flow controller. The session entry isthus created which is then passed to the session memory controller (thispart not illustrated in the figure).

Prior to getting the session in the established state as in step 13, thecontrol plane processor may be required to perform a full login phase ofthe storage protocol, exchanging parameters and recording them for thespecific connection if this is a storage data transfer connection. Oncethe login is authenticated and parameter exchange complete, does thesession enter the session establishment state shown in step 13 above.

FIG. 48 illustrates major steps in the session tear down flow. The stepsin this flow are very similar to those in FIG. 47. Primary differencebetween the two flows is that, instead of the SYN, SYN-ACK and ACKpackets for session creation, FIN, FIN-ACK and ACK packets aretransferred between the initiator and the target. The major steps areotherwise very similar. Another major difference here is that theappropriate session entry is not created but removed from the sessioncache and the session memory. The operating statistics of the connectionare recorded and may be provided to the host driver, although this isnot illustrated in the figure.

FIG. 49 illustrates the session creation and session teardown steps froma target perspective. Following are the steps followed for the sessioncreation: 1. The SYN request from the initiator is received on thenetwork media interface; 2. The scheduler retrieves the SYN packet fromthe input queue; 3. The scheduler sends this packet for classificationto the classification engine; 4. The classification engine returns theclassified packet with appropriate tags; 5. The scheduler, based on theclassification as a SYN packet, transfers this packet to the controlplane processor; 6. Control plane processor responds with a SYN-ACKacknowledgement packet. It also requests the host to allocateappropriate buffer space for unsolicited data transfers from theinitiator (this part is not illustrated); 7. The SYN-ACK packet is sentto the initiator; 8. The initiator then acknowledges the SYN-ACK packetwith an ACK packet, completing the three-way handshake. This packet isreceived at the network media interface and queued to the input queueafter layer 2 processing; 9. The scheduler retrieves this packet; 10.The packet is sent to the classifier; 11. Classified packet is returnedto the scheduler and is scheduled to be provided to the controlprocessor to complete the three way handshake; 12. The controller getsthe ACK packet; 13. The control plane processor now has the connectionin an established state and it passes the to the storage flow controllerwhich creates the entry in the session cache; and 14. The host driver isinformed of the completed session creation. The session establishmentmay also involve the login phase, which is not illustrated in the FIG.49. However, the login phase and the parameter exchange occur before thesession enters the fully configured and established state. These datatransfers and handshake may primarily be done by the control processor.Once these steps are taken the remaining steps in the flow above may beexecuted.

FIGS. 50 and 51 illustrate write data flow in a target subsystem. TheFIG. 50 illustrates an R2T command flow, which is used by the target toinform the initiator that it is ready to accept a data write from theinitiator. The initiator then sends the write which is received at thetarget and the internal data flow is illustrated in FIG. 51. The twofigures together illustrate one R2T and data write pairs. Following arethe major steps that are followed as illustrated in FIGS. 50 and 51together: 1. The target host system in response to receiving a writerequest like that illustrated in FIG. 33, prepares the appropriatebuffers to accept the write data and informs the storage flow controllerwhen it is ready, to send the ready to transfer request to theinitiator; 2. The flow controller acknowledges the receipt of therequest and the buffer pointers for DMA to the host driver; 3. The flowcontroller then schedules the R2T command to be executed to thescheduler; 4. The scheduler issues the command to one of the packetprocessor complexes that is ready to execute this command; 5. The packetprocessor requests the session entry from the session cache controller;6. The session entry is returned to the packet processor; 7. The packetprocessor forms a TCP packet and encapsulates the R2T command and sendsit to the output queue; 8. The packet is then sent out to network mediainterface which then sends the packet to the initiator. The securityengine could be involved, if the transfer needed to be secure transfer;9. Then as illustrated in FIG. 51, the initiator responds to R2T bysending the write data to the target. The network media interfacereceives the packet and queues it to the input queue; 10. The packetscheduler retrieves the packet from the input queue; 11. The packet isscheduled to the classification engine; 12. The classification engineprovides the classified packet to the scheduler with the classificationtag. The flow illustrated is for unencrypted packet and hence thesecurity engine is not exercised; 13. The scheduler assigns the packetbased on the flow based resource assignment queue to packet processorqueue. The packet is then transferred to the packet processor complexwhen the packet processor is ready to execute this packet; 14. Thepacket processor requests the session cache entry (if it does notalready have it in its local cache); 15. The session entry is returnedto the requesting packet processor; 16. The packet processor performsall the TCP/IP functions, updates the session entry and the storageengine extracts the PDU as the write command in response to the previousR2T. It updates the storage session entry and routes the packet to thehost output queue for it to be transferred to the host buffer. Thepacket may be tagged with the memory descriptor or the memory descriptorlist that may be used to perform the DMA of this packet into the hostallocated destination buffer; and 17. The host interface block performsthe DMA, to complete this segment of the Write data command.

FIG. 52 illustrates the target read data flow. This flow is very similarto the initiator R2T and write data flow illustrated in FIG. 41. Themajor steps followed in this flow are as follows: 1. Input packet isreceived from the network media interface block; 2. Packet schedulerretrieves the packet from the input queue; 3. Packet is scheduled forclassification; 4. Classified packet returns from the classifier with aclassification tag; a. Depending on the classification and flow basedresource allocation, the packet is assigned to a packet processorcomplex which operates on the packet 5. Packet processor complexlooks-up session entry in the session cache (if not present locally); 6.Session cache entry is returned to the packet processor complex; 7. Thepacket processor determines the Read Command PDU and requests the readdata with a request to the flow controller; 8. The flow controllerstarts the DMA to the host interface; 9. Host interface performs the DMAand returns the data to the host input queue; 10. The packet processorcomplex receives the data from the host input queue; 11. The packetprocessor complex forms a valid PDU and packet around the data, updatesthe appropriate session entry and transfers the packet to the outputqueue; and 12. The packet is transferred to the output network mediainterface block which transmits the data packet to the destination. Thediscussion above of the flows is an illustration of some the major flowsinvolved in high bandwidth data transfers. There are several flows likefragmented data flow, error flows with multiple different types oferrors, name resolution service flow, address resolution flows, loginand logout flows, and the like are not illustrated, but are supported bythe IP processor of this invention.

The IP processor of this invention may be manufactured into hardwareproducts in the chosen embodiment of various possible embodiments usinga manufacturing process, without limitation, broadly outlined below. Theprocessor may be designed and verified at various levels of chip designabstractions like RTL level, circuit/schematic/gate level, layout leveletc. for functionality, timing and other design and manufacturabilityconstraints for specific target manufacturing process technology. Theprocessor design at the appropriate physical/layout level may be used tocreate mask sets to be used for manufacturing the chip in the targetprocess technology. The mask sets are then used to build the processorchip through the steps used for the selected process technology. Theprocessor chip then may go through testing/packaging process asappropriate to assure the quality of the manufactured processor product.

While the foregoing has been with reference to particular embodiments ofthe invention, it will be appreciated by those skilled in the art thatchanges in these embodiments may be made without departing from theprinciples and spirit of the invention.

1-17. (canceled)
 18. A TCP/IP stack providing transport layer remotedirect memory access capability for use in transporting information inactive sessions or connections over IP networks, said stack providing aninterface to the upper layer protocol functions in a host processor tocarry data traffic, and performing at least one of the hardwareimplemented functions of: a) establishing and tearing down of transportlayer sessions; b) maintaining protocol information regarding saidtransport layer sessions that are active; c) establishing remote directmemory access (RDMA) connection with a peer with the transport layersessions; d) storing said information about the memory regions reservedfor RDMA in an RDMA database; f) executing operations provided by thetransport layer RDMA capability; and g) executing security operationsfor the said transport layer sessions.
 19. The TCP/IP stack of claim 18further comprising: a) TCP/IP checksum generation and verificationfunctions; b) CRC calculation function for payload transported using theTCP/IP sessions; c) Direct data placement processing function; d) Upperlayer framing function; e) segmenting and sequencing operations; and f)functions to handle out of order packets.
 20. A TCP/IP processor enginehaving RDMA capability, said processor engine for processing InternetProtocol packets and comprising at least one of each of: a. an RDMAmechanism for performing RDMA data transfer; b. a checksum hardware forperforming checksum operations; c. a data memory for storing data usedin the TCP/IP processor engine; d. an instruction memory for storinginstructions used in the TCP/IP processor; e. an instruction fetchmechanism for fetching said instructions; f. an instruction decoder fordecoding said instructions; g. an instruction sequencer for sequencingsaid instructions; h. a session database memory for storing TCP/IPsession data; and i. a session database memory controller forcontrolling said session database memory; and a host interface, or afabric interface, or bus controller, or memory controller or combinationof any of the foregoing for coupling to a host or a fabric.
 21. TheTCP/IP processor engine of claim 20 further comprising: a. a hash enginefor performing hash functions; b. a sequencer manager for sequencingoperations; c. a window operations manager for performing windowingoperations to position packets within, and/or verify packets to bewithin, agreed windows; d. a classification tag interpreter forinterpreting classification tags; e. a frame controller for controllingdata framing; f. an out of order manager for handling out of order data;g. a register file for storing data; h. a TCP state manager for managingTCP session states; i. a CRC component for performing CRC operations; j.an execution resource unit or ALU for data processing; k. a TCP sessiondatabase lookup engine for accessing session entries; l. an SNACK enginefor selective negative acknowledgment; m. an SACK engine for selectivepositive acknowledgment; n. a segmentation controller for controllingthe segmentation of data; o. a timer for event timing; and p. a packetmemory for storing packets.
 22. The combination of claim 20 wherein saidregister file stores packet headers, pointers, contexts or sessionstates or any combination thereof.
 23. A TCP/IP processor implemented inhardware and capable of implementing transport level RDMA functions,said processor including a session memory for storing sessioninformation for a plurality of sessions.
 24. The TCP/IP processor ofclaim 23, further comprising: a. an RDMA mechanism for performing RDMAdata transfer b. at least one TCP/IP processor engine for processing IPpackets; c. a session memory for storing session information; d. atleast one memory controller for controlling memory accesses; e. at leastone media interface for coupling to at least one network; and f. a hostinterface for coupling to at least one host or a fabric interface forcoupling to a fabric.
 25. The TCP/IP processor of claim 24 furthercomprising at least one of: a. a packet processor engine for processingpackets; b. a classification processor for classifying IP packets; c. aflow controller for controlling data flow; d. a policy processor forapplying policies; e. a security processor for performing securityoperations; f. a controller for control plane processing; g. a packetscheduler; h. a packet memory for storing packets; and i. a connectionmanager or session controller for managing sessions.
 26. The TCP/IPstack of claim 18, wherein the host processor has transport level RDMAcapability for enabling TCP over IP networks, said processor including aTCP/IP stack providing TCP/IP protocol termination and origination, saidhost processor comprising: a. an RDMA mechanism for performing RDMA datatransfer; b. at least one TCP/IP processor engine for processing IPpackets; c. a session memory for storing session information; d. atleast one memory controller for controlling memory accesses; e. at leastone media interface for coupling to at least one network; and f. a hostinterface for coupling to at least one host or fabric interface forcoupling to a fabric.
 27. The TCP/IP processor of claim 26 furthercomprising at least one of: a. a packet processor engine for processingpackets; b. a classification processor for classifying IP packets; c. aflow controller for controlling data flow; d. a policy processor forapplying policies; e. a security processor for performing securityoperations; f. a controller for control plane processing; g. a packetscheduler for scheduling packets; h. a packet memory for storingpackets; and i. a connection manager or session controller for managingTCP/IP sessions.
 28. The TCP/IP processor of claim 7 wherein saidprocessor operates in multiple stages, comprising one or more stages of:a. receiving incoming IP packets; b. providing security processing forsaid incoming IP packets if necessary; c. classifying said incoming IPpackets; d. scheduling IP packets for processing; e. executing dataand/or protocol processing operations on IP packets; f. providing directmemory access for transferring data/packets to or from the memory of asystem external to said processor; g. executing protocol processingoperations on data or commands forming IP packets; h. providing securityprocessing for outgoing IP packets if necessary; and i. transmittingoutgoing IP packets onto a network; wherein each of said stages iscapable of operating on different IP packets concurrently.
 29. TheTCP/IP processor of claim 24 wherein said processor operates in multiplestages, comprising one or more stages of: a. receiving incoming IPpackets; b. providing security processing for said incoming IP packetsif necessary; c. classifying said incoming IP packets; d. scheduling IPpackets for processing; e. executing data and/or protocol processingoperations on IP packets; f. providing direct memory access fortransferring data/packets to or from the memory of a system external tosaid processor; g. executing protocol processing operations on data orcommands forming IP packets; h. providing security processing foroutgoing IP packets if necessary; i. transmitting outgoing IP packetsonto a network; wherein each of said stages is capable of operating ondifferent IP packets concurrently.